Each different currency has it's own hash rate, it's own difficulty, value, etc etc,  JUST like bitcoin.

When you signed up, IF you put in an address for these different currencies, you will be mining them along with your bitcoin.
If you did not put in an address then you will NOT be mining them.

No worries though simply re register with a different name and then add your wallets for these different currencies.
Then you can take payouts Of them to your respective wallets.

If you do not want to have to search out / download / install/ get working all the different coin type wallets.  You can goto an exchange like vircurex for example and create a wallet there.
The money goes there, and you can do what you want with it then.

Aaron