My first step would be to either look into task manager or Process Explorer ( Process Explorer
) to see what's eating the CPU. Once you found the culprit, we can go from there. The 6150 should not be the general problem - except for certain games.
Also have a look into Device Manager whether anything is flagged in yellow for lack of proper drivers
Btw: Windows 7 upgrade is not such a good idea. A clean install is a lot better. You can do that even with an upgrade disk.