You should start mining LiteCoins since it's more profitable.
Here's the list of pools http://www.askminers.com/mining-pools-list
But I suggest notroll.in for startder since you can withdraw at 0,1 LTC and that shouldn't be a problem even with that computer.

You can later change LTC for BTC and in the end you'll have more BTC than you would earn by mining them.

just my 2c