my power suppy is really crappy and I suspect its why my system is getting lousy fps in BF2142. It used to run fine in 1280x1024 with all gfx settings on high without chugging but lately its been really chugging on medium to low settings on 1024x768.

Ive got a 7800GS 256mb AGP gfx card and it says it wants 400w, I did a PSU calculation of all my hardware and it said I needed 330w, My PSU is some cheapo one I got with a barebone kit and its probably not even 300w.

Would this be responsible for my declining performance, its gotten worse lately since the PSU fan has been acting up.

I watch the voltage of my cpu and it will drop when i open a program, so does the AGP volts.

When I removed a few things using power from my m/b (firewire/USBs etc) and my 3dmark settings went up, no overclocking was able to raise it, the removed power using stuff is the only thing that raised the 3dmark score but its still below what it should be for this card.

It should get 8000~ but Im only getting 6300~

Simple answer. If you have exhaustively explored Malware, Spyware and Virus' and you have fresh built your PC then yes, the PSU is under-powered for your needs and yes, it can effect the GPU if it isn't getting enough "juice". I would say it is better to replace the PSU than to start overclocking (and risking the integrity) of your graphics card.

An underpowered PSU will affect performance quite dramatically, get a new psu, go with a branded make such as antec or enermax.

Another thing to note is benchmark scores will vary and can be affected by just about everything in your system, it's also not a very good way of measuring real world performance,