I have a friend who is having problems with attachments in outlook 2007. He is sending JPG files from outlook but an ASPX file is being received at the other end. I have tried looking at this myself and have found that if I select open at the download prompt, It runs some script that has been attached to the pictures which continuously opens up window after window, whereas if I select save, II can open the zip file normally. I would normally suggest that this is the behaviour of a virus but neither his McAffee or my AVG pick anything up. I believe there may be a piece of malware on his system but am concerned that his McAffee is not picking it up. I can view the e-mails with the attachments fine in his sent items so it appears to be something in the send process that is altering the attachment. Any suggestions on what I can do to help my friend? I'm at a loss. I thought about trying spybot but if McAffee and AVG don't find anything, I'm not sure where to go from there other than a complete format of his PC.

Software/Hardware used:
Outlook 2007, Internet Explorer (not sure which version)