Teefer.sys is a driver level sensor. Interestingly Sygate recognizes the issue of a corrupt teefer occurring frequently in Windows ME.
Where the system will fail to boot or throw a memory dump and the error message DRIVER_IRQL_NOT_LESS_OR_EQUAL.
Sygate's recommended fix is to do a clean un-install. First un-install SPF via the un-install wizard then reboot. Then once up please do the following.
Run a system search for anything related to Sygate, Sybergen or SPF and delete it.
Using Regedit locate and delete the following folders or registry keys if found.
HK_LOCAL_MACHINE\software\sygate technologies, Inc.\Sygate Personal Firewall
Finally search and delete in windows “Teefer.sys” (windows\system32\drivers\teefer.sys) and “Wps.dll” (windows\system32\wps.dll)
Reboot and be sure the built-in firewall ICF is disabled before reinstalling.