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jamesgl
- Do you have a backup of your library folder, if you do then restore it, in its entirety.
- Did you try restoring the database (thats metadata.db in file speak) - see attachment - it may take a while.
- Calibre itself doesn't keep anything in the Registry, the only thing that's there is what the MS Trusted Installer puts there, and IMO that's best left alone.
All the settings etc are either in its configuration folder or the database(s). Could be there's something in there that's gone awry (but I suspect its database) - Preferences->Miscellaneous->Open calibre configuration directory will take you to the folder.
Close calibre and pack everything there into a zip and put that on your desktop. Then delete everything and start calibre it will take you through the Welcome Wizard, you may have to remind calibre where your library(s) is/are located.
If you have to take option 2, the zip you saved on your desktop will useful in resetting your preferences etc - come back to us if you need guidance.
If the answer to 1. was no, then you ought think about having a backup of your all your data.
BTW - IIRC Revo Uninstaller Free doesn't see 64 bit software, and IMO the pay4me Revo Uninstaller Pro isn't necessary with Win7, so I wouldn't waste my money buying it - I'd give it to Kovid
If you want to give the registry an occasional dusting then I suggest CCleaner - many similar tools are far too aggressive and are liable to break things (i.e. they're chainsaws, CCC is a fretsaw).
BR