The process name of OE is msimn.exe. Are you sure it isn't in the ctrl-alt-del list?
In stead of reboot, try logoff/logon. OE is a user process, not a system process, so it should be ended by the logoff. That's faster than rebooting.
Every once in awhile I try to open or change users on Outlook Express and it will not open. After a bit I get an error message that says outlook express cannot open because it is already running. There is no icon in the tray for OE and if I press CTRL-ALT-DELETE it does not show OE is running. the only way I can get into OE is to reboot system. Running XP checked for vir/malware but everything looks clean. Any ideas how to fix??? THX.