To uninstall Softimage, I don’t bother with the Control Panel, I just run %XSI_HOME%\Setup\uninstall.bat. Control Panel is the “best” way, but I haven’t had any problems with the quick-and-easy batch file.
The batch file is also handy for silent uninstalls.
BTW, there’s also a setup.log file in that same folder; could be useful if you want to check what product key or serial number was used for the install:
Destination: C:\Program Files\Autodesk\Softimage 2012 SP1\ Product Key: 590D1 Serial Number: 123-12345678 Licencing Method: Stand-alone License Servers: