A blkindex.dat error means that the block index has been corrupted or can't be opened. However, the block index is not part of the wallet, and can be deleted without removing the funds in your wallet.
With that in mind, try this:
- Open
%APPDATA% in file explorer. Do this by pressing Windows + R, then typing %APPDATA%.
- Open Roaming\Bitcoin.
- Make a new folder in there called 'old block files,' or something similar.
- Move every file in that folder except wallet.dat into the old block files folder.
- Optionally, delete the 'old block files' folder.
- Start Bitcoin 0.11, and your computer will redownload the block chain. This will take a few hours.
What's the exact error message? – Nick ODell – 2016-04-11T04:15:14.160
Runaway exception – kym – 2016-04-23T05:02:31.537
A fatal error occurred. Bitcoin can no longer continue safely and will quit. EXCEPTION:ST13runtime_error CDB() : can't open database file blkindex.dat, error22 C:\Program files (86)\Bitcoin\bitcoin -qt.exe in runaway exception -@Nick ODell – kym – 2016-04-23T05:14:29.103
@kym That looks like an error from 0.7, as blkindex is no longer used since 0.8. What happens if you just start the new version? – Pieter Wuille – 2016-04-24T08:11:06.377