Please help me find the bottleneck

Hi guys, I'm both new to PC's and this forum so I apologize in advance for any excessive idiocy or ignorance. I'm trying to figure out exactly why my frame rate drops in some games. I've been checking the resource monitor as soon as the frame rate drops and the only thing that seems to be maxing out is my hard drive. However, it's a 7200 RPM drive which is the same as a lot of the test models on gamespot for example, and they claim to get over 30 FPS with Crysis Warhead. Here are my PC's specs:

Hard Drive: ST3250410AS ATA Device
CPU: AMD Athalon 64X2 Dual Core Processor 5200+, 2700 Mhz
GPU: NVIDIA GTX 260
Memory: 2gb DDR2

Any suggestions on even how to diagnose what the problem is would be great. I don't know how to measure my GPU's performance (I'm a noob, remember). Thanks for any help,

Jake

ok, sounds good. I have vista 32 bit so I think the most it can do is about 3.5 gb of RAM. Ill try that first. Do you think another hard drive would make a big difference?

Having said that

Another thought... what games & settings are you trying to play? For instance, if you are trying to max out Crysis at 1920x1200+ resolution with that rig, then everything is a bottleneck.

Hard drive/OS upgrades are great ways to blow lots of money for insignificant or irrelevant performance gains. 3 GB RAM will be more than enough with that setup. If you really want to dump money into the system, then I'd start with upping the processor to a nice Core 2 or Core 2 Quad, and then either going SLI 260s or maybe upping to a GTX 280/295.

At that point it might make sense to up the OS so that you can raise the RAM to 6 or 8 GB.

More thoughts... check your drivers to make sure they are up to date and make sure you don't have junk running in the background. Those ideas are basic but they help a lot if you haven't checked em already. You could also try to O/C the graphics card and see if that helps. It's pretty low risk and easy to do in the nVidia control panel (or with whatever software the 260 uses).