blank screen !?!?! please help ? x(

so about 2 weeks ago on my computer the screen kept flashing on and off a couple times but when i went to eat dinner and came back it was jsut blank and didnt know what the problem was. so the next week i turned it on and the screen was on but only for like 5 minutes and shut off, i looked for ways to fix it on other sites like unplugging then plugging everything in and it worked for about 40min to about 2 hours then shut off and never showed anything again till today...
but im wondering whether its my computer or my graphics card?
or does anyone have a solution?
please and thank you for the help =]

1gb ram
nvidia geforce 128mb

pretty much all that i know ><
Hi Jan.....
I think that the graphics card has problems or the display you are using might get cracked.You please tell that what type of display you are using whether it is of type CRT or LCD.So I can suggest you the precise solutions.CRT might have problems regarding its tubes.Anyways stay connected.