512MB DDR - About 5 months ago
NVIDIA GeFORCE 7800 - About 2 months ago
1GB RAM DDR - About 2 weeks ago

And all that new hardware was piled on the original, and most likely barely adequate to begin with, power supply? If that is the original PSU that came with that computer, that could certainly be a big part of your problem.

Use the eXtreme PSU Calculator Lite to determine your power supply requirements. Plug in all the hardware you think you might have in 2 or 3 years (extra drives, bigger or 2nd video card, more RAM, etc.). Be sure to read and heed the notes at the bottom. I recommend you set Capacitor Aging to 30%, and if you participate in distributive computing projects (e.g. BOINC or Folding@Home), I recommend setting TDP to 100%. Then look for brands listed under the "Good" column of PC Mechanic's PSU Reference List. Don't try to save a few dollars by getting a cheap supply. Digital electronics, including today's advanced graphics cards, need clean, stable power. A good, well chosen supply will provide years of service and upgrade wiggle room.

As far as determining the brand of the computer, look for a label on the back.

Hey all, I appreciate you guys helping me, but I'm gonna save up for an Alienware... But I still need this fixed.

it said 282W, so I'm guessing thats 282 watts. I need to go and practise piano now, and when I come back, I'll have a Brand and Model of my PC.

Just a quick reply here:

Not enough power.

You need a new (larger) PSU.

but atm, it only has a 512 RAM, original HD and original CDROM Drive

So what happens when you turn it on?

but atm, it only has a 512 RAM, original HD and original CDROM Drive

And a power hungry video card!!! Even with the cheapest, low-end 7800 card I can find, the PNY 7800GS, the recommended MINIMUM is a 350 Watt supply. Specifically, which card do you have?

You need to eliminate the PSU as the problem. The best way is to swap in a known good one that meets the PC's power requirements.

Going back through this thread (I have not looked at your others) there are still several unanswered questions:

What is the precise model number of this machine?

did you take the CD Rom out of machine before trying to clean with white spirits?

Having followed all your threads here could you please clarify and condense all your issues?

So what happens when you turn it on?

As for the model of the machine, use Everest as previously suggested, or use CPUz - in particular, we need the information on the motherboard and the CPU.

1) Gotta look into that soon
2) Of course
3) I don't have any issues atm... Just this one.
4) It just powers on, but the screen is blank and theres no beep at the beginning.

"... and when I come back, I'll have a Brand and Model of my PC."

Still waiting on this info......

"It just powers on, but the screen is blank and theres no beep at the beginning."

No beep is not a good sign. It indicates one (or more) of three main elements;

Power Supply is (partially) burned out. (It may have enough "power" left to light up some LEDS or spin a fan, but one or more of the main rails are shot. Probably your case with the info supplied thus far.)

Motherboard is damaged. (This can happen with a bad/under-powered power supply.)

CPU is damaged. (Same as above.)

this is the back of the computer

Model/Type: UT0W - C02
MS WHQL No: C5P919830

And therres S/N and PID and P/N, but I dont think you need that...

Mobo is GiGABYTE GA-BSIMLN

Didn't get very far with the Model/Type info;

http://www.google.ca/search?hl=en&q=UT0W+-+C02&meta=