Hi,
Here’s are the answers to your questions:
1. I would not suggest that you use Windows XP 64bit especially if this machine is built and designed for gaming. Support for drivers, as you stated, is limited and some games will not run at all on Windows XP 64bit.
2. As for the amount of installing and reinstalling retail media, no there is not a limit, but the key that came with the media can only be activate on 1 system at a time. The same key cannot be used to activate multiple systems at the same time. If the customer has an OEM (Original Equipment Manufacturer) copy of Windows XP you will not be able to use your current copy of Windows XP on the system he just built as OEM copies of windows are for one machine and one machine only. It cannot be transferred or moved.
3. The Windows XP OS (Operating System) for 3rd party hardware manufacturers are not new or different from any copy of Windows XP except that they are preinstalled OEM versions that cannot be moved to another system. System builders do not sell OEM copy’s either. Furthermore, no manufacture of hardware even sells Windows XP as an option at this point in time for new hardware.
I would suggest you that you review the options and features of Windows 7 64 bit as it is a much better and more stable operating system. As for your Windows XP games, you may need to check with the manufacture to see if they are compatible with Windows 7 prior to making a decision.
Hope this information is helpful.