try the various compatibility settings
which Windows 7 offers (especially with Windows XP SP2-SP3 and Windows 2000 SP4 modes), and run them with administrator privileges
, also when you're installing them.
If this doesn't work, another way to solve this issue is to create a 32bit virtual machine
on your pc. In internet you can find a lot of freeware which allow you to do this. The virtual machine will completly emulate another pc into your real Windows 7 64bit. The performance of the virtual machine should be very slow, but if you're going to run only old games it should not be a problem. try it