CPU upgrade, which one to get

Hello all,

I am rebuilding my old Compaq Presario desktop that has an ASUS M2N68-LA (Ivy) motherboard and AMD Athlon 64x 2 3800+ CPU. I recently replaced the hard drive and upgraded the RAM from 1GB to 2GB. I also upgraded from Windows Vista Home, to Windows 7 Home. This is where I have run into trouble. I cannot update Windows or load any other software without the computer freezing and throwing up a weird screen image. I had also replaced the power supply that had burnt out, which is a 250W ATX 60Hz. I have done research as to which CPU I can upgrade to, but am confused as to whether I can go over the 4800+ and 2.0Ghz? Also several articles I have read said to update the BIOS? Any help would be greatly appreciated.


Thx Babynurse