If it's those MSN Messenger popups this should stop them.
This is for Windows XP so if you don't have that you will
can modify it to yours.
CANCEL WINDOWS MESSENGER POPUPS:
(Windows XP)
Click Start > Control Panel >
Click Administrative Tools >
Click Component Services >
Double click Services Local >
Scroll to and Double click Messenger to bring up the
Messenger Properties >
Under the General Tab find Startup type and in the drop
down menu
Click on Disabled > click ok
Good Luck,
Gene