I have downloaded the ISO file but not sure how to use it to install the windows 7 which is an upgrade version Many thanks

While searching in internet I found 3 ways of doing this thing. I will explain all of them here.
1st Method: (The simple one) * Requires a valid ISO image.
Download Microsoft's official tool to install Windows 7 from your USB stick.
Links below:
From CNET: http://download.cnet.com/Windows-7-U...?tag=mncol;pop
MS Store: http://images2.store.microsoft.com/p...B-DVD-tool.exe - Microsoft Store Info Here.
To install the Windows 7 USB/DVD Download tool:

1. Click to open the Windows 7 USB/DVD Download tool installation file.
2. When you are prompted to either save the file to disk or run it, choose Run.
3. Follow the steps in the setup dialogs. You'll have the option to specify where to install the Windows 7 USB/DVD Download Tool.

Note: You need to be an administrator on the computer you are installing the Windows 7 USB/DVD Download tool on. The tool requires the Microsoft .NET Framework version 2.0 or higher.
2nd Method: (Reliable method, Supports multiple types of image files) Requirements:

• USB Flash Drive (4GB minimum)
• Windows 7 Image file
• UNetbootin ( download it from here).

Now insert the USB drive, run UNetbootin, and select Disk Image as ISO( or select the type of image file of which you have).
Browse your local drive for Windows 7 that you downloaded and click Open.
Now Select Type as USB and choose the drive.Once done, it will look like a bit similar to the screenshot shown below.

Click OK and it will begin extracting all installation files to the USB drive. The whole process will take some time(10-15 minutes), so have patience.
Once the installation is complete, reboot your computer. Now while your system is starting up press the appropriate button(usually F1, F2, F12, ESC, Backspace, or Escape) to bring up Bios Boot Menu. Change the startup order to boot USB by default, usually you will have to press F6 to move the selected USB device on top. Once done, save changes and restart the system.
3rd Method:( Try this if both above methods are not working) Using Ultra ISO application.
1) Download the free UltraISO trial by clicking on this
2) Start UltraISO as administrator
3) "Burn" the iso image to the USB stick by following these steps
With UltraISO:
- Open the image of Vista/Win7 with UltraISO
- Under BOOTABLE tab choose WRITE DISK IMAGE
- Choose your USB stick under "Disk Drive"
- Choose a method (It's recommended to use USB-HDD+)
- Press Write
PS: Make sure to change your BOOT order in BIOS to boot from your USB drive first.

Still using Windows XP Professional for me its still Microsoft's Crowing glory thats until Windows 7 came along.

If you are unsure about upgrading then why not download a 90 trial version from technet available until 31st December 2010 in ISO format.

http://technet.microsoft.com/en-gb/evalcenter/cc442495.aspx

(takes about 3 hours at 124 KB/sec)



What you will need;

• Java Runtime Environment (latest version 6 update 20)
  
• Windows Live account - also comes with Hotmail and 25GB FREE
• Windows 7 Upgrade Advisor checks for compatibilty issues
  
• Microsoft Easy Transfer Wizard to transfer your files to Windows 7
  

Don't delay if you don't want to get left behind Microsoft will stop supporting XP by the end of 2010, this means that there will be no more offcial service packs; updates or patches provided.