My system is basically:
Asus P5k mobo
Core 2 duo 3.0ghz (conroe) CPU
4 sticks of ddr2-800 ram
Asus 8800gt (512mb) vid card
soundblaster (pci)
10krpm raptor 160gb hd
7200rpm wd 160 hd
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I have a coolmaster case that came with a 500watt psu. The computer has been running pretty well with all games so far with an occassional stutter in call of duty 4.
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Is the 500 enough and is there any program or way to monitor how much power is being used?

The "Power Supply FAQ" at the top of the forum has a lot of good info. Total watts don't matter so much on recent systems; total +12V amperage is the key. Also, the quality of the power supply design and construction affects how stable the voltage is -- low-end (bigger "tier" number) supplies have much more fluctuation in the voltage, which can lead to hard-to-pin-down system flakiness. Lower-end supplies are also more likely to fail, possibly causing damage to the MB/CPU/etc when they do fail.

Coolermaster make pretty good PSUs, so I would say that 500w is enough. If you do some serious upgrading, then I would recommend upgrading to a 750w, its much more than you will ever need.

Well I am using a Zalman ZM-MFC2 which has a powere meetr which is pretty helpful in determining what leevl of power u are using, i have a MSI 790fx, with a fx-62, [2] hd 3870 in corssfire, ht omega striker sound card, [4] 1 GB DDR2 OCZ, [2] 15k rpm SAS drives on a lsi logic SAS raid controller, in an antec 900, i used a 850 watt sliverstone psu, like 85% of the time i use less than 220 watts [already errored on the side of safety] only when running 3dmark06 it uses maybe 389 watts, so its safe to say u can turn it down.

I wish their was some software or something that could monitor that, like way of gadget like in vista, or something...