Hi, I have a HP Pavilion Elite m9000t that's listed with a 350w power supply with the following components:

Core 2 Duo E6750 2.66Ghz
4 Sticks of RAM (2x1GB DDR-667, 2x512MB DDR-667)
320GB SATA HD
Nvidia Geforce 8600GT 256mb GDDR3
PCI-E 1x TV Tuner
DVD+-RW with Lightscribe
Few USB Devices (Printer [guessing that doesn't draw power via USB], Mouse, Ipod sometimes, charge digital camera sometimes).

I put it into the extreme calculator and got 220w (put 1 80mm fan).

I'm thinking adding another HD would be fine. Correct? I don't know how good this PS is.

I'm also thinking this will not be able to handle an 8800gt. Correct?

Thanks a lot.

Running a 8800GT might be pushing the limits of that PSU. Adding another hard drive should be fine though.

Hard drive you should be fine. As for the 8800gt it may not, your going to have to check your 12v rails on the psu. They will be on a sticker on the side of your psu. I believe you need about 20a on the 12v rail(s). If you have multiple 12v rails, note that you don't add them together. Example say 12v1 is 10a and 12v2 is 10a, you wouldn't have 20a on the 12v rails but something more like 16-18.

Thanks for the help, guys. Ordered a 500GB HD. Gonna stick with the 8600gt.