URGENT HELP: Hard disk Full (Virus)

Hi

I run a little network with windows server 2003 installed on my server and clients running XP.
Recently I discovered that on my server I am running Low on my C drive and so i deleted some files to solve the peoblem. Later a client complained that his C drive is 0 byte whilst he has not much things on his drive.

I went through his files and folders but nothing I could find. After serveral research I discovered that its kind of a virus but there is no solution on the Net. Please help as its spreading accross my network.