find the disc and boot from it try start up repair from there if that fails try system restore if that fails then there should be an option to enter the recovery of the machine and reset to factory defaults ( if it is branded and not a home build that is) do not suppose you created your own image at all?
If you need windows ISO for your key or to boot and attempt recovery they appear to be available here
http://www.techfleece.com/2012/10/18...ally-for-free/ ensure you get the right version