Just to clarify
Have you tried booting it up in safe-mode? Does it work then?
It's [possible] that it might not be windows, but instead be an external program that executes automatically during windows startup, or it could be a corrupt driver for a third party device. Best to check these out before going through all the hassle of getting it repaired. If it doesn't boot up in safemode, then yeah it's almost definitely windows.