Others can advise you on those games in 7, but if you really want a dual boot, then get your XP installed, unplug all other drives but your XP and Win7 target drive, boot from the Win7 installer to use Custom>Advanced tools to format and install Win7 on its target drive.

Win7 installer will configure the dual boot menu.

As far as moving your XP into your new build, why not follow your friend's suggestion to try a repair install and see if it will run as well?

If it was Win7, you would see quite a show, a cascade of drivers changing out, punctuated by requests for restarts.

Normally XP will just not startup, but since the repair install for XP (unlike 7) is done from boot, you can jumpstart it by booting from the XP installer, then don't choose R for repair, but continue as though you are going to install until it finds your XP installation and THEN asks if you want to repair it, say yes. It's worth a try.