hi i need to buy a new power supply because i am upgrading my computer i am upgrading to a pentium 4 . on ebay i saw a 400w power supply would this be powerful enough. also if i bought a power supply with 500w and the computer only needed 400w would this blow the system?

No the greater Watt rating is nothing to worry about, just leaves you some head room for adding devices later on."BARGIN SHOPPING" for a power supply is not wise at all, you are after all going to get what you pay for, if what you have found on E-bay is truly a quality supply do go for it, however you may be wise to find a good deal on a really good supply. Someone will come along and give a suggestion on the best deals out there right now just keep checking back.......... Keep the old stuff running

Just be aware there are a number of different configurations and you need to ensure the PSU you get will have the right connectors. ATX old style has 20pin mobo connector. ATX P4 has that plus the extra 4 pin. I believe ATX2 has a 24 pin mobo connector as well as the 4 pin. Make sure you gat a good quality suply that will suit your motherboard. I used to have a signature but it disappeared and I just couldn't be bothered writing another so please feel free to ingore this.

The rating only states how much power your PSU is rated to give. If your computer only needs 240W, then that's all the PSU will give it. The PSU is the backbone of your computer. You don't want to skimp out on the PSU. If it blows, it can take out your other components too. I'd read reviews on PSU's as well...I once bought a PSU that was louder than a vaccuum cleaner...you probably want a silent PSU ;-)

http://www.firingsquad.com/guides/power_supply/default.asp http://www.sysopt.com/articles/PSU_Perspectives/index.html http://techreport.com/reviews/2003q3/psus/index.x?pg=1 http://www6.tomshardware.com/howto/20021021/index.html Asus A7N8X-X 1800+ @ 8.5 x 200MHz 768MB PC3200 2.5-3-3-7 Asus A9550GE/TD 128MB WinME/WinXP Pro