I have an 0.8.8.3 wallet (3 files : xxx.bin, xxx.bin.keys and xxx.bin.address.txt) and opened it in 0.8.8.6. I got following message "You had been using a deprecated version of the wallet. Your wallet file format is being upgraded now" and everything looks fine.

Can I upgrade this wallet to a deterministic wallet with seed or do I have to create a new wallet with seed and transfer the coins ? I think I remember reading somewhere you could upgrade an old wallet without seed to a wallet with seed, but I'm not sure.