|I had the same problem, with the same IMEDIA by packardbell that you have, and I'm using it to type this, and it's fine now!!!|
The first thing I did, is purchace a cheap (Power Supply Unit).You can pick one up from ebay for less than £20/$32.60c-(keep this as your spare)!
Alternatively, intall one from a 2nd PC if you have one. If the problem persists, (NEVER!!!!) take it to an so called "trained proffesional/Technician". Because you could buy a high spec PC with the money you will save. Many would rather continue taking your money than tell you what's wrong with it. Dose your PC bleeb when starting up? If it cuts out before this, it's your PSU.
Yours might not last 1 year, it says 250w on right? That's no good. You need at least 400watts.
If there's a sticker on you motherbaord it will normaly have the model and/or serial number on it. if not, get your magnifying glass and look on the front somewhere near the CPU or edge of your board. Once you have found it, either google search or try the manifactures website for a table of the diagnostic bleeps and what they indicate/mean. If this is no help, having had the exact same problem myself,with the same machine, I found it was the crapy PSU that was cutting out the power. Then give your hard drive a(gentle)shake,see it if it rattles(I replaced the HDD) because it was broken, and the system could not locate it. If you have removed the CPU fan at all, then apply the best CPU cleaner/thermal paste you can buy. I had removed the cooling fan, and it was over heating, In both cases that worked. If non of that works, then i'm sorry, but it's time for old faithfull (process of elimination). I'm certain it's hardware causing this. One part/device at a time. Look for the defective or worn-out part/device.If you put something in there, before this happend(ie a graphics card), you should remove it.
Best of luck. Post how you get on.