Cpu upgrade

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.

The 6000+ is the best you'll be able to use in that motherboard. It's also still for sale at Newegg: http://www.newegg.com/Product/Product.aspx?Item=N82E168...

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.

Also, the new proc would be a full 1GHz faster--a 50% improvement in raw clock speed!