need help

It's a Hp, a420n. As I said before, I don't really know much about computer and the thing that freaks me out is that something could go wrong and I might not be able to get my monitor to work at all so er, before I try the "Bios", Ill wait for further commands or unless I need to go test it out now ;(

Uh, It's on a window xp, pavilion... perhaps I could a list of stuff I might need in order to help detail out my computer? x)

It stopped responding when I made my computer sleep for awhile and then it wouldn't come back on so I had to switch to my computer monitor jack instead of the GeForce. Now I don't really know much about the whole computer thing and how it all works so I could really use a lot of details and step by step. :\