is it cheaper to repair or replace the tower of a desktop pc?

If the power light turns on, then, there IS power. The motherboard does get power as the power light is fed through the motherboard.

Disconnect the power cable.
Open the case and make sure that the power cables are correctly connected to the hard drive(s) and other components. Make sure that all cards are properly seated in their connectors.

If the computer don't even start to the POST screen, it means that the video card is not working (in this case, you'll hear some regular BEEPS) OR your RAM is bad (you'll hear some regular BEEPS) OR that some other key component is dead (no sounds at all or irregular beeping).

If it's the video, replacing it is the solution.
If it's the RAM, replacing is easy and relatively cheap.

If it's something on the motherboard, then, it's probably impossible to repair and you need a new computer.

In this case, it's cheaper to get the parts and assemble it yourself. That way, you can reuse several components, like the case, power supply, hard drive(s), video card and any other extention card.

Electro
April 2012