So you have two PC's. The old one with enough
BTC in the wallet, and a new one to which you might have sent five BTC.
I would proceed like this:
Stop all bitcoin programs on both PC's
Make a backup of the wallet.dat file on the new PC, call it wallet-dat-new
Make a backup of the wallet.dat file on the old PC, call it wallet-dat-old
Install version 0.8 of bitcoin-qt on the new PC. This version is fine for you, in case you know about the fork yesterday. You're not going to mine.
Start bitcoin-qt 0.8 on the new PC and let it run for a minute so it has downloaded a little bit of the blockchain.
Stop bitcoin-qt on the new PC.
Copy wallet-dat-old to wallet.dat on the new PC
, overwriting the existing wallet.dat (you have a backup of it too)Start bitcoin-qt on the new PC and let it download the complete blockchain. This will take a while. Your amount of BTC should appear while it is downloading.
You now have the latest bitcoin-qt program with your BTC in it.
Once you succeeded, you'll get instructions to check for the five BTC
Which brand car are you looking at ?
Good luck!