Windows 7: boot disk failure after hdd disconnect

stupid i know,

but i managed to unplug my internal hdd in error while it was running.
i had 2 identical 500gb hdds installed, 1 of which i wanted to upgrade for space reasons. While the pc was running i unplugged the sata cable to try to identify the one that DID NOT have the OS on, doh!

anyway i eventually found out which of the 2 was the storage one rather than the c: drive with he OS on and replaced it with the larger capacity drive.

now the pc boots to an error message of BOOT DISK FAILURE.

I have found that leaving my original win 7 install disk in the dvd allows the pc to boot fine with no intervention.

but how can i get the pc back to boot ok without the need for the Windows 7 install disk in the dvd drive?

i am running win 7 home premium (v6.1 build 7601 sp1).



cheers

Try this method: MBR - Restore Windows 7 Master Boot Record

Thanks for your help, however i tried the bootsect.exe method above but it hasnt solved it, i also tried the bootrec command but couldnt get it to work (the bootrec command link is dead).

any more ideas?