I had initially installed Windows 7 then Ubuntu 9.10 on a singe SATA disk. Later I added an IDE disk and plugged in the SATA DVD drive and can no longer boot into Windows 7, with the error:
error: invalid signature
Press any key to continue..
Back in Ubuntu I could see that my inital SATA disk was now sdb with the IDE disk as sda – I think this is where my problem stemmed from. So I tried:
sudo update-grub
and received errors such as:
Found Windows 7 (loader) on /dev/sdb1
grub-probe: error: Cannot find a GRUB drive for /dev/sdb1. Check your device.map.
So then I tried:
sudo grub-install /dev/sdb –recheck
Which seemed pretty successful and re-running:
sudo update-grub
Successfully built the menu again with no errors. So I rebooted and …. success!
Useful info about Grub 2 here and here.