black screen :( computer issue

[Nice]

hello everyone, i'm having this weird problem. When i start my computer everything goes all fine but after like 10 sec my screen goes black but computer still runs perfectly. So heres the weird part... If i turn off my monitor and then turn it back on, the screen starts working again but once again shutsdown after like 3 sec. and i could do that forever. So the way i handle the situation right now, is restart my computer like 30 times (not overreacting) and then it works fine...But yeah, spamming restart is bad for my nerves and my computer.

Win XP Nvidia geforce 8800

PS: I tried upgrading my drivers

And yes...sorry... this is a serious thread