My Dell Desktop Will Not Boot Up

Hello,
Ok here's what happened I was playing Age of Empires 3 and I was moving my feet back and forth and turned the thing that my Computer was plugged into off so i turned it back on and the Dell screen loaded just fine but when it got to the part where the Window's XP screen is suppose to come up the Back light on the Monitor come's on but the screen stay's black, I do not have the XP disk to reinstall Window's and i herd that you can do it without a disk Just to let you know I have Windows XP from 2005 i don't know if that make's a difference please wright on possible solutions thank you