Advice on new pc power supply



Hi !
I have just bought a Acer Aspire M3802. I need to buy a new power supply with at least 450w so i can run an ati radeon hd 5770.
I dont trust the guys at pc world (they have let me down before) who say i can buy any old power supply.
So i thought id run it by the real experts.
Is this true? i would really appreciate your recomendations.
Many Thanks !
They're not pulling your leg this time.
The only thing you need to be mindful of is the depth of the replacement unit.
The oem unit's in mid towers are usually only 140mm deep and there isn't much room for anything larger.
Check out Antec Earthwatts units, up to 500 watts they are the same depth as the oem.