u mean it ask u to insert some sort of disc or boost device ?
if so, u need to insert the Win7 CD, restart, press F12, select boost from CD, choose repair ur window in the window installation. if u are still lucky, it will fix the boost issue. if not, there are 2 situation :
1. For some reason, ur entire Window disappear >> clean re-install
2. Your storage is dead, this is very bad >> buy new one >> clean re-install
wish u luck with the start-up repair