Here's a comprehensive list of freeware that will run on Windows 7 64-bit systems:
Best Free Windows 7 Software.
Where a native 64-bit application is currently unavailable in an important category, a suitable 32-bit alternative is provided.
Perhaps the program you're having installation issues with can be replaced with a 64-bit version of a program from this list. I have found a few good programs off of this list before and it can be very helpful.
You can also check out the
Free Software Database here on this forum. Many good programs listed there.