You have stated that you have found the evidence on a disk laying about. So the questions are: (1)What made you open and view the contents of the disk. (2) Who as access to the area the disk was found in. (3) Who shares the network with you (4) Have other people on the same network been compromised. (5) Is your part of the network safeguarded by your own password system. (6) What firewall are you using (7) What operating system do you have on the computer (8) Do you do regular updates and checks.
Perhaps provide some of the answers, then there might be some solutions or suggestions available?.