Question about new Power supply ?

[VEBouto]

Hi, is it OK to replace the 450w power supply in my computer with a 420W power supply. I have a brand new 420w thermaltake PSU which i haven't used yet and i thought that i would replace my 6 year old 450w unit which seems to be getting a bit noisy.
My PC is a 3.2Ghz, pentium 4, 2G memory and will be running the Motherboard, 2 DVD Roms, a floppy drive, 160GB Hard drive, a Video Card and Audio card. Thats it.
I'm asking if it will be OK cos i have read a few threads on the net regarding changing power supplies and a couple of people have said that you should replace your current power supply with one of either the same wattage or higher.
All replies welcome.
Thanks.

[ranchhand]

Assuming that you haven't added a lot of power-consuming peripherals you will be fine. The power difference between them is so slight that it won't make any difference. Just FYI - the noise that your old PS is making is probably the bearings in the exhaust fan beginning to wear, not from the actual unit itself. Those fans can be replaced quite cheaply. You have to remove the PS (easy, four screws on the rear of the casehold it in), remove the cover (3 or 4 screws hold the cover on) and the fan is right there. Chances are it just plugs in to a socket. I have done it many times.

[redwudz]

Just a safety comment about replacing a PS fan. Let the unit sit unplugged and idle for a few hours. High voltages aren't the safety problem but PS capacitors can store quite a bit of current, enough to melt the end off a screwdriver and give you a nasty burn, besides possibly destroying the PS. Be careful what you touch in there with metal tools. Even if the fan leads are soldered to the PS circuit board, you can splice the cut leads together with crimp on connectors or solder and shrink tubing. Don't use electrical tape as it can unwind in the heat.

[ranchhand]

Good points.

[VEBouto]

Thanks for the replies. What do you guys classify as power-consuming peripherals. What kind of stuff?.

[Noahtuck]

Thanks for the replies. What do you guys classify as power-consuming peripherals. What kind of stuff?.

Anything you have added that uses electricity that did NOT come with the PC originally.
Dvd/Cd drives, hard drives, usb drives that use power from the USB port, etc etc etc

Or you could use an online PSU calculator,

http://www.antec.outervision.com/

http://extreme.outervision.com/psucalculatorlite.jsp

There are lots of different ones online but they are pretty much the same.

[Nelson37]

You are fine, do it.

6-year-old PSU I would not bother to replace the fan, especially if you already have a new unit.

[ranchhand]

Actually, when I junk an old computer I tear out the PS fan and throw it in my shop drawer. They usually move a good amount of air, and are generally quiet. I use them in builds as additional air movers occasionally. I have had pretty good success with them. However, just this week I finished my first unit using a water-cooling setup, and I don't think I will ever look at air cooling again.