Why does the initial blockchain download get stuck part way through?
Restart OS, restart Bitcoin, try forwarding port 8333 on your router to your machine.  If there is no progress after that, you might consider deleting all the files in your Bitcoin data folder except wallet.dat (if you have made any transactions, deleting wallet.dat will make you lose your Bitcoins). If you just want to use Bitcoins casually, or don't want to wait for the client to sync, you can consider using an eWallet.