#1) An OEM restore/reinstall disk typically will be configured to revert a given machine from a specific machine family (ie: same make, series, and model) to as-produced-and-shipped condition, including machine-specific drivers and settings, along with machine-vendor-specific software. BIOS and motherboard issues
may - often but not always will - render such a disk unsuitable for use on any other machine than one of the same series and model as that for which the disk was intended. An additional consideration is that OEM-installed Windows operating systems are not intended or licensed to be installed other than on the original machine.
The short version - could work, often does, sometimes takes a little fiddling, and sometimes won't work at all - you might find the install routine either will not initiate or will procede only so far before stalling and/or aborting, or, perhaps worse, will install but will fail validation, registration, and activation.
#2) Linux is gotten on to any machine the same as any other OS is gotten onto any machine; it is loaded from a bootable install disk.
#3) Commercial, packaged, pre-made releases of Linux, such as Debian, Mandrake, and Redhat, while not free are readilly available through retail outlets both online and brick-and-mortar, and come "ready-to-install" - just pop in the disk, open it or reboot, select "Install" and follow the prompts. Commercial versions also typically come with manuals and have at least some official support from the licensing vendor. A variety of versions, some purporting to be identical to commercial versions, are available for free download, but generally require a bit of fiddling before they're ready to be burned as a bootable install disk. If you wanna go the download route, research your options well before making your choice, and be aware no vendor support will be available; you're pretty much gonna hafta resort to the boards and foriums of the Linux community for help and advice.
Be advised also that apart from game compatibility issues of which you apparently already are aware, it can be quite entertaining to track down Linux-compatible device drivers and peripheral-specific software - you could be in for a bunch more fun than you might suspect.
#4) Release Candidate 1 of Windows Vista is available for download - big download, mind you - but once properly burned as a bootable disk it is a fully functional Operating System (if such may be said of anything based on any Windows platform :wink:

:wink: ). It will require registration and activation once installed, and the free activation license will expire shortly after the scheduled release date (Q1 '07) for the final retail version of Vista, requiring that you obtain and enter a paid activation key to permit continued use and necessary updating/patching of the Operating System. When necessary, the required final release key can be obtained via eMail - for a fee, of course, but if its any consolation, the fee will be discounted compared to purchasing the full, packaged version.