Laptop wont go to desktop?

ok so yesterday it was working fine, and i turned it off, i went to the store and came back to turn it on, it worked nomaly, when it went to the '' please wait....welcome'' screen, after that it is supposed to go to the desktop, everytime i go to that all it shows is a black screen. i keep retry-ing it! it keeps showing the black screen! what do i do? ( p.s, i have an hp mini laptop)