Update: Well, the problem seems solved now, and thanks to everyone for your advice :). Rather than repeat what I said in my comment, do check it out if you've replied to my call for help. Thanks again!

This is a computer problem that has been bugging my desktop PC and me (me mostly - the machine seems pretty happy, and sometimes I think I hear sniggers). Well, the problem is, it boots up and then freezes irrevocably (resetting is the only recourse). Nothing out of the ordinary yet, considering I'm running Windows XP, but it freezes at any point from bootup to a fully logged in session in Windows XP. Sometimes it even fails to POST. Sometimes there is just a white line across the screen and the rest is black.

Here's what I think could be causes:
1) The monitor (it's a Phillips Brilliance 105 - circa 1996 I think) is too old. But does an old monitor cause the system not to boot or to freeze? Anyone had experience with old monitors? Will it blow up in my face?
2) The power supply's dying. Possible. But it's a new one and it should be way above requirements.

I don't know how to debug (or perhaps I'm just too lazy), so I'm casting about hoping someone would bite and tell me that they have had this exact same problem and how to solve it.

PS. I'm ready for any suggestions that my monitor is truly dead or highly dangerous in its current state - gives me an excuse to get a new, bigger (it's 15 inch) one.