lmfao....dont worry. even an 8800gt will run on a 300 W. the "minimums" on the specs info stuff, is just to prevent total noobs from blowing up their comp. they just want to be secure.
even a GTX 285 under load only uses max 350. that 350 includes the procesor, ram and hard drive as well al though that comp is a barebone comp. you have a pentium 4 which uses quite a bit of power. im pretty sure it will work perfectly fine tho.