if you reformatted your harddrive then there should be no more files.
Indeed. Did you reinstall a program that has the infection? That is the only way I can think to have reformatted and got a reinfection. DAT files and CABs alone cannot let the intruder back in, it's the server that lets them in. However, I can understand after being hit with something like that one becomes a bit awry about things.

As with all compromises like this, take deep breaths and do not panic. Sacn with the Cleaner as these good folks have said and run netstat -a to see if the server is still listening. I doubt it is, but it's better safe than sorry.

Good Luck