I'm thinking about purchasing a new desktop computer to run Mach 3 on and all the new computers I've came across have the new O.S. windows 7 installed.. Does anybody know if mach 3 will run on windows 7 ??

Works great! One word of caution though. Most new PCs that come loaded with windows also have a ton of other crap already installed. Make sure you get a PC that actually comes with a real Win7 CD/DVD so you can reinstall the OS without the 'extras;.

Will Mach 3 have any problems with Windows 7 64 bit operating system? 

It probably won't work, unless you use an external motion device like the Smoothstepper.

Someone was reporting getting Mach to run on a Win 7-64 machine by using XP compatibility mode. The LPT driver is not signed so it will not run in 64 bit mode.

You might could boot into "Test Mode" and get it to work.  No need for signed drivers in test mode.