Re: linux or windows?
Windows XP is better supported for games. Yes, you can run 2 OS on one system. This where partitioning the hard drive kicks in. Default user accounts is Admin and for Linux, not sure. You don't have to have mulitple accounts to run two OS. You can run dual boot options from the beginning of power up to see what OS you want to boot into and that's it.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?