Anyway, program uninstsap.exe should exist in the <drive>:usrsap<SID>SYSexerun directory. Execute it to remove SAP.
If that isn't working, perform all steps manually:
1. Delete the SAP services. You can use program sapstrtsrv.exe to do so.
2. Bounce the system.
3. Remove everything under <drive>:usrsap<SID>
4. Open the registry and delete registry key: HKEY_LOCAL_MACHINESOFTWARESAPSIDEnvironment
This was first published in April 2005