My questions are: 1)Will the AMD Athlon II X4 640 Propus 3.0GHz work with my MOBO? 2)Is there better CPU to use with my system? 3)What will have to be done after changing the CPU? Will the bios have to be upgraded, what about the OS, will I have to reload or will it work with all my files remaining intact?
1. the good news is your mobo has an AM2+ socket so the Athlon II may be able to work. The bad news is the HP BIOS may not support it. Your best bet would be to find a HP forum and see if anyone has already tried to install an AM3 CPU into that motherboard.
2. see above, another question to ask a HP forum.
3. having the latest BIOS is always a good idea, you can download it from the HP web site. You wont need to reload any software or re-install Windows.