Tools > options > advanced > system startup. Untick 'run on system startup' & apply. If it keeps popping up after that, it's probably a virus. See point 4 here
WARNING: Viruses on the network you should be aware of

There's a link to Norbiesworld within that thread. Go to his site & register, he'll help you to get rid of the virus! Make sure you scan a file with your AV program before opening it.