380 watts will run a pair of hard drives, 2 gigs of RAM, any processor you want (other than an Intel Extreme Edition, AMD FX, or Intel pre-Conroe), most graphics cards (only one high-midrange board, so no 7950GX2, no X1900 or 7900GTX, but a 7900GT would be fine), but NO OVERCLOCKING.
PSU power ratings are more of a marketing tool nowadays. The only reason I have a 550W PSU is that I have an X1900XT, I will be overclocking in the future, and I might want to get an X1900 CrossFire or DX10 graphics card.