Well it doesn't sound like the hard drive to me, which is the good news, because although one of the cheapest components and easiest to replace, you have reinstalling time to consider and no data at the end of it.
It's going to be something fundamental, such as RAM, CPU, video or motherboard. Does it beep differently during POST, or even at all? That will indicate the fault better, depending on the make of your motherboard.
The age of the PC makes a huge difference, but I guess you don't use it for anything stressful, so...
CPU - CPU? Fuck it. Bin it and buy a new PC. Seriously, the only cheap CPU is an old CPU and they have the shortest shelf life of any of the components, so if you need an old model, you may be onto a loser.
Be aware, the components above can all put each other at risk, meaning blown RAM, may have damaged the board, etc. Keep a very close eye on billing. Two component failures plus labour could easily be north of £150 and that's better spent on a new PC, even second hand if necessary.
Good luck.
Bad : It will cost me 256 $CAN to fix it
I am assuming your current PC is quite old.
Bought it in march 2007 (so it's fairly new) and just finish paying it a couple of months ago.
How much are you being charged for labour?
It a 2 years and 3 months old computer that was bought new.
What are the specs of it? Do you know? (CPU make, Motherboard make, etc.)