Besides system specifications a good description of when you see the freeze ups might help here. You may have seen a bad install of the OS or could have a hardware related problem. It could be simply a need to remove and reinstall video or sound drivers if you see these while running a game or software.
Sounds more driver related then anything. Sometimes the next update will fix problems with one catalyst version. I've run into that a few times with new cards seeing the latest already on the disk itself.
You are running a 64bit edition as well. Did you run into any problems with 4gb in when going to install that edition? Often you have to reduce the memory down to 2gb until the 64bit edition is on.