In my experience the following method solves almost any windows boot issues. Try it out.
- Insert your Windows installation or recovery CD
- Boot to System Repair Options
- Open command prompt
- Type BOOTREC /RebuildBCD and hit ENTER
- This rebuilds the Boot Configuration Data (BCD) file
- Type BOOTREC /FixBoot and hit ENTER
- This writes a new boot sector to the system partition
- Type BOOTREC /FixMBR and hit ENTER
- This writes a Vista / Win 7 MBR to the system partition; does not overwrite the existing partition table
