Computer won't start properly (black screen)

[Sonitex]

My neighbor had a garage sale and I found an old desktop computer with windows xp on it. I tested it there and it worked. However I accidentally pressed F1 during the screen with the white text and the input options (F1 , Enter, or something like that). I panicked and pulled the cable out. Now the computer doesn't seem to boot at all. The lamp that shows if the disk is running is not blinking.
Any chance of rescue? I really hoped to find a good old desktop pc that my dad could use.......so sad....

 

[margibso]

When it tries to boot are you just getting a black screen or are you getting the Motherboard post at least.

 

[Sonitex]

Just a black screen.