If you're getting an error message about it not being able to run on a 64-bit OS, you simply won't be able to run them. You can install XP mode for Win 7 (I believe you need win 7 pro or ultimate to do this) and then run the old games from the virtual OS. It's not too complicated as long as you're willing to do a little research.
An exact error message would certainly help diagnose exactly what is happening though.
XP era games are all 32 bit applications, so they should run in the 64 bit environment. You can try running the installer in Windows XP compatibility mode if you are having trouble. As said above, if you have Windows 7 Professional or Ultimate you can download Windows XP mode, which runs XP in a virtual machine. Problem with that is advanced graphics driver features tend not to work well in that mode, as XP mode is meant more for legacy enterprise software, rather than gaming.
If you are talking about Windows 3.1 95 or 98 titles, that's where it can get problematic. If the games are really old, you can try running them in DOSBox. If it is a 95/98 title, you may have to track down a copy of that old OS and try running the games from 95/98 in a virtual machine.