You said "gaming", and that does mean Microsoft.

I certainly won't try to steer you towards Vista, but XP is no longer supported, which means that new games may well not run on it.

Windows 7, the follow-up to Vista (and rumored to be the reason why more effort has not been put into fixing Vista) is coming out soon. If you can hang on just a bit longer, that will likely be worth it in the two-to-three-year time frame.