Check your mobo docs to see max cpu frequency.
If you have the lga 775 socket I'd suggest a core 2 quad like this $150 one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115207
If you have the money go for the $280 one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115041
If you want only the best, go for this $340 one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115130
For graphics card I prefer radeon hd over any other.
A good one would be this $175 one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814161348
Best of the best would be this $277 one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102914
They sell em more expensive, if you prefer overclocking.
You most likely will need to buy a new PSU, or at least have a 450W for the entry models, and at least a 550-600W supply for the best card and cpu.
Hi SungOdra, As Prodigit suggested, your basic pool of CPUs are socket 775 processors. There are many of them to choose from, although Intel has started to discontinue some of them as their new models are introduced. Of course they can still be found at retailers and there is nothing wrong with them.
The main factor that may limit your choice is your mother board. Pentium 4 CPUs are among the first ones that use the socket 775 platform, so the later models such as the Core 2 Duo and Quad series may not be compatible with that mother board, or more correctly it's BIOS. If you can still find documentation for that PC, you may be able to find which CPUs were available as options for it, since manufactures sometimes offer upgrade options to their basic PC platforms. If for example Core 2 CPUs were offered as upgrades, then it is more likely that any CPUs of that kind will work with that mother board.
Another possible limiting factor of that mother board is it's Front Side Bus (FSB) speed, which from the specs you posted, seems to be 800MHz. Many of the Core 2 CPUs can run at FSB speeds of 1066 or 1366 MHz. I think that those CPUs can be used at your 800MHz FSB speed, but the overall performance of that combination will be lower than those CPUs are capable of. The FSB speed of 800MHz will be a "bottleneck" that may limit the overall performance that could have been gained with a high performance socket 775 CPU. Therefore you may not achieve any more performance from the very best CPUs compared to ones that are somewhat below them in potential performance.
As modern GPUs/video cards function more independently from the CPU and mother board system than in the past, there is less concern with their interaction. What is most important regarding video cards is what interface your mother board has for them. Being from 2006, it might have the AGP interface, rather than the PCI-E interface used exclusively today. I cannot tell from the specs you posted which interface your mother board has. That will be a major factor determining which video cards you can use. You should find out what that interface is, and post that information for us, as that is likely more important to overall gaming performance than the CPU.
