I've got a question that just popped up in my head...

If my system would need a 450 watt power supply and I would use a 400 or 350 watt instead, what would happen? Would the system shutdown? Could it be harmful to a system?

Bad things happen...
Sometimes the power supply sometimes other devices suffer...
If it shuts down in the middle of a write to your hard drive... Bad, bad...
Even if it cools down and comes back on that glitch will stay on the drive.

There are websites that can help you determine the correct power supply.
I linked to one in another message on this board, you might search for it...

I dont have those links on this PC... Sorry..

im not advertising but antec psus are really good and reliable i think for an avergae user 350 watts is good. but if you ahve new componetns or many components installed it is always better to have a high capacity psu.

Im not concerned for myself. I recently bought a ultra xconnect 500Watt modular power supply and its great.

Rather than guess you can use this website to calculate what you need.

Buying a 500 watt when you really only need 350 is a waste in initial expense and on your monthly electric bill.

Here is the link...

http://www.jscustompcs.com/power_supply/

They dont even have my cpu and video card lol. Not up to date.....

Thong Ispector...thanks for the web site info, I know how to use Ohms law...I just couldn't find the wattage figures to calculate my power requirements. This site gives accurate figures with a comfortable fudge margin.