Ok thanks, I have the XP disc. So I can clean install Win 7 on a new Hard Disk whilst keeping XP on my existing hard disk, both on the same PC?
If you would like to dual boot Windows XP with Windows 7, then you will need to purchase an OEM or a Retail license of Windows 7. To qualify for an Upgrade license of Windows 7, you need to have a legitimate copy of an OEM or Retail license of either Windows XP or Windows Vista. Though, once you have installed Windows 7, you will no longer be able to use the previous version of Windows that you used as the qualifying product for the upgrade:
Microsoft said:
*Snip*
14. UPGRADES. To use upgrade software, you must first be licensed for the software that is eligible for the upgrade. Upon upgrade, this agreement takes the place of the agreement for the software you upgraded from. After you upgrade, you may no longer use the software you upgraded from.
*Snip*
Also, depending on weather you have an OEM or Retail license of Windows XP, once you have installed Windows 7, those same licensing restrictions will then also apply to Windows 7.