if you have a 100 PSU, then chances are you won't be - if you have a 150 PSU, as long as you aren't running anything really funky, then it might actually work. If you have something higher than that, then chances are it will work, unless your setup is really intense - in which case I think 250 is just about standard, and works with just about everything. I am a freak and I have a 431w PSU, but its kind of overkill... especially since I don't have a working processor