Litecoin Core software problem

Hi all,

I am a newBee here.
Yesterday I downloaded the Litecoin Core 64-bits version on my portable hard-drive. It works fine.And I bought some litecoins.
Today when I try to re-open the Litecoin Core. It indicated that it is the first time to use it(But I already used it yesterday and I already bought litecoins!). What should I do? I installed the Litecoin Core in my laptop. And it is synchronizing now.
After finishing the synchronization. I assume the litecoin volume will be zero.
How to get the litecoins back from my portable hard-drive? (Just simply replace the wallet.dat?)

Thanks in advance!

let it sync…set a passphrase and make a backup…also read more on using wallets on wiki…
also make sure you have it installed correctly to your c drive or where ever you want…if the wallet is not saving the chain data then you application data is not being stored correctly I would guess…might need to change something in your folder options…let it sync completely then encrypt it with a passphrase and make a backup then try again