You have a couple of problems, your board uses an nVidia chip set and going to Windows 7 you probably needed to upgrade the BIOS on the mobo and the chipset which is responsible for your CPU and the coCPU as well as your SATA and other devices, so upgrading both of these is very important.
The other issue is the freezing more than likely is your ATI 4350, once you get your drivers
and BIOS squared away you can tackle downloading CCleaner andDriveSweeper. Go to Start>Control Panel>Device Manager>Display Adapter and uninstall the driver
for the ATi 4350 and then uninstall the 4350. Run CCleaner and DriveSweeper and have them clean anything associated with your nVidia 7100 and the ATi4350, once completed go to ATi and download Caatylist Control Center Suite and Drivers for the 4xxx series Version 10.3 (10.4 and 10.5 had issues and I have not tested 10.6, 10.3 is very stable).
Extract the CCC but don't let it install just note where it is.
Shut down the PC then cold boot it, it will find the 4350 and load MS drivers, run CCC and it will find and update the 4350. Once you have done all this most of your issues should be behind you. I say most because you have a lot to do before we'll know.