How to reinstate missing bootloader entry


My machine was successfully dual booting Vista and Windows 7. Until in a *stupid* moment I deleted the boot loader entry for Vista. So the machine boots to Windows 7 fine, and the Vista installation itself is fine, but I just can't boot it. Any tips as to how to recover from this situation ? It was a pretty clean Vista install, so I could just re-install as a last resort, but if there is an easier way I'd take it