Suspicious file

Hello. I have CIS running on Windows XP (SP3) and a couple of times when I have started the computer up I have received a transient message message from CIS that it has detected a suspicious file. However the message does not last long enough for me to record the details of the suspicious file or where it is. I think that the site began /hard… I have done a full CIS scan and a full Malwarebytes scan and neither has reported any problem. I there anything else that I should be doing? Thanks.