I have partitioned my C drive and now have a 2nd

You will need the XP CD to "downgrade", and you must re-partition the hard drive, and re-format the new partition before installing XP.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

Greetings.
There is no direct path to downgrade Vista to XP. You can’t simply insert the XP installation CD media into the CD-ROM drive and hope to ‘upgrade’ and replace the Vista with Windows XP usual install routine because Vista won’t allow it to be overwritten. XP will treat Vista as ’superior’ operating system and refuse to install over it. There’re actually few options available instead of completely uninstall Vista as listed below. But if you decide to downgrade from Vista to install XP, there is also a simple guideline that you can observe to ensure that the migration goes smoothly.
Option 1 – Dual Boot:
It’s by far the easier and best method to run XP instead of Vista if you have another partition or hard disk. Simply boot up any XP setup media and install XP into different partition or hard drive than the Vista installation. Once completed, you can choose to boot up either XP or Vista, and has the best of both world.

Option 2 – Virtual Machine:
Install VMware Server or Virtual PC 2007 (both free) or any other virtualization software, and then install Windows XP into the virtual machine
environment. You will get XP which runs inside Vista, with minor compromise on speed, performance and have to go through Vista first on every bootup.

Option 3 – Format the Hard Drive, Wipe Off Vista and Install XP:
For those who totally fed up with Vista and just want XP, or prefer a clean installation of OS has only this option to rely on. To downgrade to XP from Vista, you have to basically delete the whole hard disk that installed with Vista, and start anew with XP. Here’s a simple guide and procedures that you can try to follow to switch to XP. However, each system configuration is different, so you may have to adapt the steps to suit your own need.

1. Download all drivers for your system for Windows XP from the manufacturer’s website(in case if you don't have the CD/DVD installers). Copy the drivers files to a USB flash driver or external hard drive or burn them to CD/DVD.
2. Find a Windows XP installation CD (should be pretty easy to find or else you can search in torrent sites such as Demonoid to download via BT network such as uTorrent and BitComet or search and download via ED2K network client such as eMule. You can also use Volume Licensing (VL) CD, retail (FPP) disc, or system builder hologram CD provided by Microsoft.
3. You will also need a XP product key even if you legally can downgrade from Vista Ultimate or Business edition. The Vista serial number won’t works with XP. (try to search for XP product key on web).
4. Backup to USB flash disk, external portable hard disk or CD/DVD every data files and any other things such as documents, downloads, pictures, movies, programs and etc that you need and want to keep. You can also create a second partition with disk management utilities such as Acronis Director or Partition Magic, and then move the data files to the new partition.
5. Ensure that also you have CD or DVD setup media for the software applications that you want to install and use after wiping off your system from Vista.
6. If your OEM doesn’t provide you with recovery CD/DVD discs and Windows setup media discs (it’s because they’re stored in the hard disk in hidden location), you may want to burn a copy of recovery CD to CD/DVD first before you proceed, just in case the hidden partition is lost and you want to recover your computer to original state. (How-to Guide: IBM/Lenovo ThinkPad recovery CD)
7. If the system has SATA (Serial ATA) hard drive, locate the driver for SATA controller and put it in USB flash drive, diskette or CD first. If you have PATA (normal IDE) hard disk, simply go to BIOS CMOS to disable SATA or Native SATA mode if you don’t want to install XP on SATA hard drive. Else, you can also create an XP install disc with the SATA drivers integrated by using tool such as nLite.
8. In the BIOS, also set the CD or DVD optical drive as the first boot device in the boot sequence.
9. Put in the Windows XP installation CD into CDROM drive and boot up the computer by using the CD. You probably need to press a key when prompted with “Press Any Key to Boot from CD…”.
10. If you’re using SATA hard disk with driver on external media (not integrated into XP setup disk), remember to press F6 when you see the message at the status base: “Press F6 if you need to install a third party SCSI or RAID driver…” during the very initial stage of setup to load the SATA driver so that the SATA hard disk can be recognized.
11. Run through the setup wizard at per normal. However, when prompting for where to install Windows Vista, delete (by pressing D and then confirmation), create and format the Vista disk drive or partition (if you have multiple partition). And then choose to install on that just formatted partition or hard drive.

IMPORTANT: If you choose the wrong hard disk or partition with data to delete, you will lose your essential data.

Note: If the setup does not allow you to delete or format the Vista partition or drive, you will need to find a third party software that can recognize and read NTFS filesystem to clear the drive or partition first.
12. Enter any product key for XP. Vista product key will not work.
13. If you own a legitimate Windows Vista edition that allows for downgrade (See Vista downgrade rights), call Microsoft after performing the clean install of Windows XP Pro to activate the XP installation. Notify Microsoft that you’re downgrading from Vista and require to activate XP Professional or other version allowed newly installed. You won’t get a new Windows XP product key though. You will have to read out the long Installation ID plus your original Vista serial key, and Microsoft will provide an activation ID that will make the XP usable.
14. Install the drivers for your system devices.
15. Reinstall any software programs that you want to use.
16. Move back the data files and documents.

Thanks

Format Your HDD firstly, using any boot CD like Hiren's boot or similar. Then install XP. The drivers You can download from Compaq site. But REMEMBER! Backup Your data and make a restore DVD FIRST!

If you have a Windows XP Pro installation disk, put it in the optical drive, restart your computer, on startup, go to BIOS settings (usually press [Delete] and set the optical drive as first boot device. Save changes and exit. When the computer starts it usually says to press any key to start from CD. Press any key and the windows installation will start. Make sure you format C: and you will downgrade to Windows XP Pro. If you want to upgrade to Vista again, you will need to know the keyboard sequence to start Vista from Its partition or have Vista install disk.

well dont boot through vista as it thinks ur downgrading and the micro$oft never thought of that!!

good news just put in your disk boot through your bois and presto it will work!

if still garanteed do nothing otherwise format the hard drive including the recovery drive then install xp.vista is ??.this is easiest way.if still garanteed try going to where you bought it ask them to put winxp on.hope this helps.

there are 2 solutions:
1-format your h.d.(if you don't need any file inside)
2-upgrade to vista, copy your important files then downgrade to xp and format the drives.

The easiest way is to reformat the hard drive using the harddrive software,which may be downloaded from the HD website, Then do a clean install of Win Xp  with the OS install CD.PS leeacve the D partition alone in case you want Vista back as some point.

you cannot downgrade from Vista to Xp unless you format your hard drive or install xp on another partition check your device manager for yellow marks on sound devices and update your sound drivers

First, why are you downgrading? Unless you have a particular piece of software that you HAVE to have that doesn't work on Vista, you shouldn't downgrade. Windows XP is outdated, and very soon won't be supported by Microsoft. So unless you have some overwhelming need to have outdated software stick with Vista.

Having said that... If you still want to go ahead with a downgrade to XP, first you'll need a copy of Windows XP and a serial number for XP.

(Note, everything on your computer WILL be erased so make sure you do your backups before you continue!!!)

1) Put the Windows XP CD in your computer and restart it. If your computer is set up to boot from CD, it should start automatically.
2) "To setup windows XP now press enter"
3) Agree to the licensing agreement
4) Choose whichever drive you want to install Windows on and press enter
5) Choose "Format the partition (Quick) and press enter
6) Press "f" to format the drive
7) It'll do the install then after a reboot it should show Regional Option, click next
8) Put your name in and click "Next"
9) Enter your 25 digit product key (Windows XP Key) and click next
10) Enter whatever you want for your computer name. It could be "Desktop" or "Laptop" or "Family System" whatever you like. If you're installing XP Professional, you'll also see a spot to type in a password to get into windows. You can leave it blank if you're the only one using it, or password protect it so no one can get in. (Then Press Next)
11) Make sure your Date/Time and Timezone is correct then press Next
12) "Typical Settings" next.
13) (IF XP PRO) Choose "No" then type in WORKGROUP
14) It should start windows after you've done those steps and you can register with Microsoft and create additional users at this point (All self-explainitory).

You might want to print this out if you're going to go ahead with the install.