|fixboot and fixmbr will NOT fix the registry and the system will not boot.|
Odds are the partition is not marked as active which is another reason you won't boot.
If you read the article on changing drive letters it says "Changing the drive letter of the system volume or the boot volume is not a built-in feature of the Disk Management snap-in."
In other words you can not change the boot or system drive letters. Again it comes back to the drive letters in the registry.
What was h: is now c: yet the registry still listes h: for source.
Either put the 20gig back in or run a repair install. Doing anything else will only result in disaster.
A one sentence question will result in a one sentence answer.