Depends on the PSU ratings, watts aren't the most important thing, its amps. Anyways, which 400 watt PSU do you have, some will be more than enough, others will be borderline, depending on how much other stuff you have in your PC (Drives, USB devices, etc.).
Most likely it will be enough, but if you post which brand and model of PSU you have, we should be able to give you a lot better answer.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>
I recommend you buy one of the following.
1) Antec True Power 430w or better.
2) Fotron Source 400w or better.
A generic just isnt going to cut it, the rails wont be stable, the amps will be low, and the watts wont be as advertised, what this all adds up to is a burnt out 400w generic power supply in a month or less, and it can possibly take your other hardware with it.
<b><font color=blue>Co-Founder and Administrator of Toms Hardware IRC</font color=blue></b>
<b><font color=red>
Server: hub1.oddnet.net
Channel: #Tomshardware
</b></font color=red>
You are about to answer a thread that has been inactive for more than 6 months. If you still wish to proceed, please ensure that your posting is original and does not duplicate or overlap any prior responses to this thread.