How to keep Bitcions when reinstalling OS from fresh I have the official Bitcoin wallet and I would like to do a fresh install of everything on the computer. How can I save my Bitcoins (and hopefully block chain)?
(I suppose you have the Bitcoin-Qt client.)

Taking a backup of the Bitcoin folder will do it. 


Copy the folder to an external hard drive of a different partition. 
Reinstall your system.
Install Bitcoin-Qt again.
Move the folder back.


Note that to keep your bitcoins, only the wallet.dat file is required. But when you copy the whole folder, you will probably not need to sync with the network again.