I recently had to reinstall windows 7 due to a faulty Seagate 1.5TB hard disc - the second time this exact model has failed for me (although the two drives were manufactured 18 months apart from each other).
After reinstalling windows, I had 2 different windows installations: the new installation on a fresh disc and the old installation on the faulty disc. I believe this may have caused "BOOTMGR" not to be installed on my new disc, instead I suspect the installer left it on the original, faulty disc.
Some time after the new installation, I removed the faulty disc which unfortunately stopped windows booting - my computer would stop just after the BIOS screens with a blank screen.
My first reaction was to dig out my windows 7 setup disc, boot from it and perform a repair. This didn't go so well because the repair dialogue couldn't recognise the windows installation!
This caused the automatic repair to misidentify my boot drive, and it seemed to get confused by an SD card that was inserted into my usb card reader, as the automatic repair attempted to update the partition table on the sd card!
I attempted to manually repair by using DISKPART to set the windows partition to drive c: and then ran the following commands which I saw in a microsoft forum post.
Unfortunately the FIXBOOT and REBUILDBCD stages both gave errors (although the scanos was able to locate the windows installation).
After removing the sd card reader, and rebooting the windows 7 install disc, the repair dialogue was now able to locate the windows installation. After doing this an earlier dialogue box popped up offering a solution (which was basically reinstalling BOOTMGR I believe).
I rebooted again but it still didn't boot! However there was now a different error message, which indicated that the first stage of the boot had succeeded.
So I rebooted again into the Windows 7 installation CD. Rather than try the automatic repair tool which I had lost confidence in a little, I entered DISKPART and ensured my windows installation volume had the appropriate drive letters, then ran the above 4 BOOTREC commands.
After this my computer booted successfully.