I'm trying to optimize my PC in any way I can. Its about time I do it but I'm afraid my computer is a little messy at the moment.

I've also been interested in Overclocking my computer and am not sure if its practical with my current setup. Which is:

Windows Vista Home premium 32bit (I'm regretting that one with the RAM thing.
AMD 64 X2 4200+ 2.21GHz
4gigs ram, I have 2gigs extra not installed and obviously only getting ~3 gig due to 32bit
Nividia 9600GT 512mb
Gigabyte GA-m57sli-S4 motherboard
All this is running on a NZXT PF400 400W power supply.

This was a custom built computer that I had someone help me with just before FSX came out. We didn't build it for FSX specifically, but we did it so that the system would be easy up upgrade but still had some speed.

It was originally built for XP and since then I have upgraded it to vista home, then home premium. That and all the random games I load/unload and the clutter that develops after a few years use, is why I called it messy.

I'd like to optimize this computer as much as I can, and I'd like to overclock it. However with a 400W power supply that may not be practical. So what can I do to help optimize the system? Ive gone through and eliminated processes and startup programs I don't need but still have like 50 processes going at any one time.

Ive thrown a lot of information out there, but I suppose the main question I would like answered is should I even consider an OC with only 400W? And how can I tell how much power my system needs?