Now a days all are using some sharewares that change the boot screens.
But after unsinstallong these there is a way of not booting also and the system kernell may be currupted.
There is a good way to solve these
use http://www.stardock.com/products/bootskin/index.asp
in this url you can get Bootskin programe for free.
after installing it go to http://www.wincustomize.com/Skins.aspx?LibID=32 for getting screens
