I have compaq sr5060an, with 2x2gb ram. current processor is athlon 64x2 3800+. Is an oldie but quiet and stable. what cpu upgrade would be suitable replacement. I am unsure of the mother board. ASUS something.
The motherboard does not matter because you have an OEM computer. Go on HP's website and look up your model in the support section. There you will find all CPUs that came with that model. They are the only ones guaranteed to work.
In my research, I found that the board only officially supports up to the 5000+ (I think). Someone at this website, though, bought Newegg's 6000+ and had it working.
Be sure to update the BIOS before upgrading the CPU.