Well, I think you have two different problems here. One your monitor or video card might be dead. Second, your problem of freezing is a little weird. Tell us more about your computer. What is your proc, ram, os, apps your running, etc.
Go into bios, and watch your temps and voltages for a while.
It would also be a good idea to run memtest86, it runs from a bootable floppy.
While you are at this give your box a good cleaning, and make sure no pieces of metel have fallen into contact.
Give the capacitors around your chip a look as well. If they are not flat on top, if they are leaking, that's your problem.
If your mobo has a fan on the north bridge, make sure it is secure, and turning well.
Endyen he's not getting boot, so how could he do memtest86 and go in the bios?
The psu may very well be at fault. If it's generic crap, then it's likely to be dead. Also, that harddrive... Samsung harddrives are crap.
If the video card is dead, the computer wouldn't boot. Computers only boot if the following components are working, CPU, Motherboard, Ram, and Video card.
So pull out everything, and just leave the CPU, MB, Ram, VID, hook up the power, and see if it powers up.
If that didn't work, take out ur ram and run memtest86 on a friend's computer. If it passes, then fine, if it doesn't, RMA it.
If ram tests fine then get a working power supply that has at least 18A output on the 12V rail, test it again with only the CPU/MB/Ram/Vid.
If your ram's fine and changing your psu doesn't do the job. Then I think your best option is to take your PC to a local shop and get them to test whether your CPU or your MB is dead or is it both. They shouldn't charge you too much just to test CPU/MB.