just copy back and spend
might be good idea to start the bitcoin client with the -rescan switch
to search for eventual transactions related to the old wallet from the time it was offline
might recalculate available balance to be accurate.
This should not be necessary anymore since 0.3.21, since information about the current best chain is stored in wallet.dat, and a rescan of the unknown part is issued when this does not wallet the block chain database. If either the last version to write to wallet.dat, or the version to restore with is older, -rescan is needed.