No, you should see how dirty the inside of your computer is, and clean it with a can of compressed air for computers, First.
Then change the power supply to a known good one, and then think about buying a new one.
Then go to the computer manufacturers website -> Support, (Or it may be listed as Support & Downloads), and go to the -> Contact Us. I would call them. (Regular business hours) Tell them you need the Restoration Disk for your computer. Look at the back of it, if it's a desktop computer, and get the Model Number. (MDL = MoDeL) You need this so you can give it to them. It's right next to the Windows Product Key.
If it's a laptop, it's on the bottom, and probably in the Service Tag.
A failing power supply will cause all kinds of problems. Half the time, they are problems that mimic software problems. Like Disk Boot Failure. This is because the registry files are corrupted. http://en.wikipedia.org/wiki/Windows_registry The other half varies, but most of the time, the computer operates for a while, then turns off.
Finally it won't boot up, (Start) at all.
Inside a desktop computer are Electrolytic Capacitors. These are small aluminum 'can's, (Kinda' look like a small pop can) http://en.wikipedia.org/wiki/File:Capacitors_electrolytic.jpg (The bottom one is an example of the style most used on a computer's motherboard, and inside a power supply)
Inside these 'cans' are three strips rolled up together.
"Aluminum electrolytic capacitors are constructed from two conducting aluminum foils. One of which is coated with an insulating oxide layer, and a paper spacer soaked in electrolyte. The foil insulated by the oxide layer is the anode, while the liquid electrolyte and the second foil act as cathode. This stack is then rolled up, fitted with pin connectors and placed in a cylindrical aluminum casing. The two most popular geometries are axial leads coming from the center of each circular face of the cylinder, or two radial leads or lugs on one of the circular faces. Both of these are shown in the picture."
http://en.wikipedia.org/wiki/Electrolytic_capacitor
The paper spacer soaked in Electrolyte, is actually Electrolytic Paste.
This paste breaks down. When it does, it forms a gas. The gas builds up, and pushes against the sealed end of the capacitor, and eventually pops the seal, of the capped end. When this happens, Electrolytic Paste begins to ooze out.
So much paste loss, and the capacitor will function as normal. When a little more paste is lost, the capacitor operates in a weakened state.
Eventually an amount of paste will be lost, and the loss will exceed what the capacitor needs, even to operate at a weakened state. When this happens, the capacitor fails all together. (Or capacitors. There may be more than one that fails)
Your computer power supply turns your household AC electricity into DC electricity. (Flashlight batteries are an example of DC electricity)
Electrolytic Capacitors used in a computer power supply, are Filters. They filter raw DC electricity, into true DC electricity.
Your computer hardware inside your computer needs a steady supply of 'clean' DC electricity. The Processor is one hardware component that needs it, and has to have it in a very close tolerance range. Too much, the processor turns off. Too little, the processor turns off.
Now envision your Operating System running, (Windows XP in this example), and everything's going fine. Suddenly the Processor 'hiccups', by turning off, then turning back on real quick. Your regustry files get jumbled up. (Corrupted)
Many a user has found that using a Restoration Disk will only fix their problems for so long. This disk restores the needed files for the Windows registry. After a given time, the problems come back.
The power supply was the problem the whole time!
How do power supply's go bad? Especially if a computer is only a year old or so?
Two reasons.
1.The owner never cleans out their computer regularly. Dust/dirt/etc, builds up, and makes the power supply overload itself. The dust/dirt/etc, clogs up the power supply fan, and the heatsink's used inside. (Also the Processor fan on the processor) Heat = Wasted Energy, and the power supply keeps putting out more power, to keep up. The Electrolytic Capacitors are the weakest link, and give out.
2.Way back, a BUNCH of bad Electrolytic Capacitors were made. They have a bogus formula for Electrolytic Paste inside. These bogus paste develops gas. You know what that does. It may not occur for weeks, or a year, (Or even more), until these capacitors give out.
http://en.wikipedia.org/wiki/Capacitor_plague
Short answer?
1.Change power supply.
2.Get the Restoration Disk and use it. Do a -> Repair
Edit:
1.Boot options are not set properly in CMOS
Been in your BIOS Setup lately, and changed the first boot device to CDROM?
No? DIDN'T THINK SO!
You would have to do this, and put a CD or DVD disk in your optical drive, that was a game, or other -> bootable disk, but was NOT your Windows XP full installation disk, or the Restoration Disk I mentioned above.
1. Boot options are not set properly in CMOS
2. Non bootable CD or CD-R in computer
3. All boot devices set are not bootable
That takes care of Number 2 also.
"All boot devices set are Not bootable?"
Like what?
Floppy disk drive is a bootable drive, even if you don't have a floppy drive. Why? Because BIOS will go down through ALL the Boot Options in the list.
It tries the first one.
No?
Okay, it goes to the next one.
HDD. Harddrive.
No?
Then it goes to the CDROM drive.
No?
Then IF the boot option is there, it goes to Internet Source.
Along the way it's going to 'see' your harddrive.
It's 'seeing' your harddrive now, it just has corrupted files on it.
Mainly the Boot files.