I did a transaction to a place that i don't have access to anymore, is there any way to cancel a transaction for that site?

Where does the bitcoin client store it's settings? Reinstalled a computer and need to file the files on the hard drive since I backed it up and windows is corrupt

By settings I mean the wallet private keys, etc

Anyone know how to reset a password to tradehill? Do they have accounts still from the past (ie. 2012/2011?)

I installed the ATI drivers but when I go to CCC it shows 3 video cards but the other two cards who as "unknown adapter".

Do I have to attach the crossfire cables to the cards? I didn't think I had to.

How do I get the other 2 recognized as 6970s?

Basically I have a 4870 when i'm currently using a 6970 is it possible to use the 4870 and the 6970 to on the same machine for bitcoin or will this cause problems? Using win 7.