I have had Windows XP on my Mac mini and you will need;
1: A windows CD
2: A windows CD Key
3: Atleast 5 gigs free I believe
4: Blank CD for mac drivers
when you install bootcamp and run it it will ask questions so just follow the instructions from there. after you partition your HD for Windows XP, I had 12gigs on mine it will ask you to restart then will automatically boot windows xp or vista, which ever you have ready to install. you'll go through the typical windows install, if you have had a windows before, you know basically what it is. then run your Mac drivers disk to get everything ready. I had a problem with mine, it wouldn't recognize my audio card. Not sure how the gaming goes but I'm sure its fine. I played War rock on mine for a bit and nothing went bad at all but thats just one game.
to boot mac os x from windows, restart your mac from windows and hold down the option key upon reboot.
I might be wrong on some info I provided so anyone please correct.
I downloaded the beta from the apple website. Just follow all the directions and make sure you have a copy of XP with Service Pack 2. It installed flawlessly on my Macbook. I had some problems with it working on my iMac but it works fine now.
As for gaming, the only game I tried was NFS: Carbon. With the 128MB graphics card built into my Intel iMac, the setting were turned all the way up or super close and it worked without a glitch. Frames looked and felt smooth. It looked nice.
Hope this helps.