Have windows xp but the licence key is partly

when you boot from xp installation cd it should start but if as you say nothing is happening there may be a problem with the cd or the drive. If you're sure it works properly you can always install your existing hard drive (the one with win 7) in another computer and format it then replace it and try again. When you format it you will wipe everything and it will be blank.

I can tell you why you are getting this error. How to fix it depends on the reason you are getting this error.
Windows software licensing means that a copy of Windows is only valid for a Single PC. As part of the installation process the Licence key is linked to the motherboard of the PC.
The error is telling you that the Licence key you have for Windows has been activated and linked to a specific Computer B IOS. You can re-activate it on that computer, you cannot install it on another computer.
There are 3 reasons you can be getting this error

• You have changed the motherboard or the BIOS chip in your machine and you are re-installing Windows. The Licence will not be accepted and this breaks MS licensing agreement.
• You are trying to re-use an existing Windows Licence on a different machine - Not allowed using a OEM (operator installed) version of Windows.
• You have reinstalled Windows on your machine using a different installation disc - this can cause confusion when re-installing an OEM version of the software. e.g. Dell branded OEM Windows will only install to Dell machines.

Assuming the licence is valid for the machine and the Motherboard you need to Contact your machine provider to get a valid installation disc - they may well charge for this service.

not possible, unless you wish to dual boot the WIndows versions ... 'you will need to place the windows XP CD, boot from this CD and format your Hard Disk and then install windows xp.
make sure you have the windows xp licence key as the WIndows vista licence is not valid for windows xp.
last but foremost .. I strongly suggest you download the three key drivers from your manufacturer for 1) Sound Card. 2) Video Card 3) Network Card and have them available after windows is installed. As Windows does not detect all drivers for your computer. Then install either your current preference of Antivirus software or use AVAST (www.avast.com) which is freely available.
check your vendors website to confirm that there is drivers for your make and model laptop or pc.
good luck ... hope this helps...

Be sure to have a correct partition to hard disk.Format the partition quick mode.

Check if this liscense expired or not? or my be this is not correct version so some boards doesnot accept it.

I’m happy to help further over the phone at https://www.6ya.com/expert/mustafa_06f84c65ab5cc745

You would need to back up your documents, pictures ect.
Format (a secure wipe would be best) your hard drive. Make sure it is fornated to NTFS.
Run/Install windows XP (remember you will have to have a licence key since the laptop came with vista)

Download all the drivers for this notebook from: http://www.acerpanam.com/flex/acerdrivers/bin/drivers.html?CFID=2232097&CFTOKEN=61504601
(best to have these on a flash drive)

and then install them.

vista includes the right to downgrade to xp - call ms support to get a licence code

If you have a genuine version of Windows with a licence key, then download and install XP Service Pack 2 from the Microsoft website. You can also request a CD copy.

If you do not have a genuine copy with a licence key, then you will not be able to re-activate Windows XP once Sevice Pack 2 has installed.

1. make sure you backup ALL data you want, after a format it is un-retrievable without the right tools
2. put your windows XP disk in the cd drive, and turn on PC
3. when it asks "Press any key to boot form CD" hit a key
4. a blue screen will appear with writing flashing down the bottom for a few minutes until you come to a menu
5. press "enter" to start a install
6.press "esc" when it asks if you want to repair old installation
7. highlight the relevant partition and press "d" to delete old partition, then "enter" then "L"
8. it will not go back to partition menu, in which case you select "C" to create a new partition and then "enter" and "enter" again
9. select "format the partition with the NTFS file system" it will now format the hard drive, then copy files, restart by itself then begin the second part of the instiallation which im sure you could manage