When do you buy a new power supply for your computer? This can be a tricky question to answer in some cases. First off, if your computer works, you don't play games on it, do graphic rendering, or anything graphically intensive, odds are, you could make do until there is a problem. If it works, don't fix it. However, if your computer was expensive or means a lot you, plus you have a bunch of add ons its probably time for a upgrade.

Lets start by talking about OEM computers. By this, I mean E machines, Dell, Gateway, HP, and anything else you can think of that is a machine not put together from parts. These computers come with a power supply that will work with only the original hardware in mind. What I am trying to say here is, if you go adding a bunch of hard drives, CDROMs, an awesome video card, ext... to your machine. Odds are, something is going to burn out. Though, you could be one of the lucky ones that starts getting strange trouble and lock ups. There are cases, were the machines' main board frys out. A loud pop and cloud of smoke is the result.

You can never have to nice of a power supply. The bigger the better. It should be rated in watts. Although, this is not a perfect scientific measurement. Or more accurately, you can't always expect everyone to be honest. So, stick with a name brand.

The biggest thing you want to look out for is the video card upgrade. A lot of the newer video cards out there suck up a ton of power. So if your gonna stick with the power supply that came with your factory built computer, go with a low end cheap video card. Sure you want it to support the latest in direct X. That is not really a indication of how much power it uses. As a rule of thumb, from every manufacturer of video cards you want to go with their cheapest model that supports the latest version of direct X. At the time of this document, the latest version of direct X being 10. If your gonna buy one of the higher end video cards, while your at it, pick up a nice power supply. It's good to know that your machine isn't gonna burn out.

One more thing thats worth mentioning, is hard drives and CDROMs. If your planning on burning videos, and maxing out the hard drive space there is a chance that your stock power supply will not cut it. The more individual drives you put in there; The greater the chance that your power supply can not handle it.