In order to uninstall TIBCO Nimbus please follow the below steps
1. Check that you have run the unwise.exe as an administrator. You should be logged in as a local admin, and you should right click on the .exe and select "run as administrator"
2. Ensure nothing is locking the install.log file by trying to rename it. - If it says it is in use, then investigate whether a user has this open, or antivirus is set to scan this file
3. In the event that the above fails to work you will have to manually uninstall:
a. Delete the Virtual directory in IIS
b. Remove the DCOM object of TIBCO Nimbus ES
c. Delete the web server directory
d. Reboot the server