Screens blank but i can see bios and startup

My screen stays grey/black. Although i can see the startup and bios.
I can also hear the computer loading things.
It happened after i quit a game last night, and i haven't seen it right since.
I installed a 512mb stick of RAM on Friday, along with a 256MB stick that's already in. It worked fine on Friday, Saturday and Sunday up till then.
I'm not sure what i can do in the BIOS, or what i can do at all.

Any help would be appreciated

 

Have you tried booting into safe mode?

 

I wasn't able to get in it but i have just booted into safe mode. I was pressing F8 too early so it was giving me the cd,floppy,hdd boot options.

Anyway, i just booted into safe mode. I could see my screen, and i've done system restore to last night and it's working fine

 

Could have been the driver messing up. Good it's working again though.

 

Yeah, an unsigned driver was installed yesterday. But i'm glad it's working now.