windows xp - What is the Cause of Random Freezing/Blue Screen/Restarting?

Problem: Freezing/blue screen/restarting happens randomly on my Desktop PC. Sometimes it just freezes suddenly. Sometimes a freezing, then a blue screen. Sometimes a blue screen, followed with a restart. Sometimes it only restarts (and then sometimes it restarts again when booting). Sometimes it's just a blue screen.

When?: Sometimes it happens when I run applications which consume too much memory (e.g.: Photoshop, watching movies, playing games). Sometimes it happens immediately after I logged in to Windows. Sometimes it happens when I'm not doing anything (usually only having one Notepad window open).

If I recall correctly, the problem happened about a year or two years ago. It happened suddenly. I didn't make any change to the computer before (didn't install new driver, didn't replace any hardware). Well, I did change the hardware, but it was long before the problem happened (was about three or four years ago).

It doesn't always happen though. Sometimes I could run the computer 12 hours non-stop without experiencing a single problem.

EDIT: Also sometimes I cannot turn on the computer. When I push the power button, the machine seems to be running (because it makes the sound, the fan is also spinning). But nothing is shown in the monitor, even after several minutes, as if the computer is turned off.

Usually I have to turn it off again, and try several times, until it turned on correctly. I'm quite sure it's not the monitor cable, because the cable is already plugged in tightly.

Question: I want to make sure and want to exactly know where the problem lies. Perhaps before I take it into service so I could (hopefully) try to fix the problem. Could anyone help me to investigate the cause of this?

Here are several blue screen screenshots I manage to take:

Computer specifications:

• OS: Windows XP Professional SP2


• Motherboard: ZX-I945LM4



• Processor: Intel Pentium 4 CPU 2.40 Ghz


• RAM: 1016 MB

Any help is really appreciated. Thank you very much.

Answer

Other possible reasons in addition to corrupt memory:

• Bad HD sectors in critical areas at the beginning of the disk. I'm almost afraid to give my usual suggestion here (buy a copy of SpinRite), because other posters think I'm advertising. But hey, in those cases it works.





• Corrupt low-level driver. See if disabling/updating drivers helps.




• I'm not sure about overheating if that may cause this. There's free software utilities available that lets your monitor temperatures, I forgot the name.




• Plain old dust. Clean the insides of your machine. At the same time pull the memory modules out and plug them back in. Especially check the fans if they're clean and run smoothly.