If I have to reinstall, is there any way to save the previously downloaded blockchain? I am not looking forward to that huge download again.
The wallet and blockchain are stored in a user data directory, and are not removed when you uninstall the software. It doesn't look "installed" anyway, perhaps you just unzipped some file.
The official download IS an installer, and is located here:
http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.8.6/bitcoin-0.8.6-win32-setup.exe/downloadIf this problem persists, you should make a copy of the wallet file (if you have used it for anything), it is located at %appdata%\Bitcoin\ and is called wallet.dat. Copy it only after Bitcoin is completely closed.
Then start Bitcoin with the command to rebuild the wallet. Press WindowsKey + R, and type in:
c:\Program Files (x86)\Bitcoin\bitcoin-qt.exe -salvagewallet (remove the (x86) if you are on 32-bit windows)
If this is a new wallet with nothing of importance, you can just rename the old wallet.dat file, and Bitcoin will make a new blank file when it restarts.