External hard drive not showing in my computer

[gerrykaz]

i have a 500G ext hard drive that doesnt appear in my computer, OS Vista, i had registry files that made my disk drive disappear from my computer (upperfilters and lowerfilters) so before deleting i was asked to back up the registry files and mistakenly backed up on ext hard drive and not desktop, in this light disk drive reappeared and ext drive disappeared, i have tried to go in regedit, but to no avail can some one help on how i can find and locate the backed up registry and delete to view my harddrive. thanx