No Signal

[RuYi]

I'm having this problem for a while now, and I have NO idea how to solve it. I'm really hoping some of you could help me out!

The problem:
All of a sudden (mostly when I'm playing a game) the computer monitor turns black saying 'No signal'. A few seconds after that the whole computer freezes, and I have to restart.
The problem doesn't always occur, sometimes it doesn't happen for a few weeks, but then all of a sudden I'm having it lots of times a day.
It seems to occur most when I'm playing a game.

The rig:
Processor: AMD Sempron Processor 3000+, 1.8GHz
Memory: 1024MB RAM
Video Card: RADEON X550
Monitor: HP L1520
Operating System: Windows XP Professional

I don't think overheating is the problem, and the drivers are all up to date.

If you have even the slightest clue of how I can solve this, please tell me, I really have no idea how to solve this, and I really need this computer for my education, buying a new one isn't an option for me.

Thanks in advance!

[Sendako]

When I had this msg once, it was simply because my display card was loose in it's slot. >_<

try cracking open your computer case to check if there are any parts that are loose/not plugged in properly, maybe? (auctually taking it apart gently, lol)

[RuYi]

I've tried that a while ago... But I'll check it again, just in case of!

Thanks a lot!