Depends on the location of this file as to whether its good or bad. monitor.exe is a service which is a part of the Microsoft Server operating system as described here
or it can be bad as shown here
. It can also be related to such programs as Ulead and Acer
What OS (Win XP/2000, etc) are you using? What type of anti-virus are you using and when was the last time you ran a scan? Did you try doing a scan in "SAFE MODE
"? Have you performed any anti-spyware scans?