Try re-installing the game again from the disc right over your current installation,carry out no other task while the installation is complete.Then reboot your system and try to uninstall again.
I am not sure what could have caused your uninstall error but the above procedure is the correct way to install and uninstall programs.You may be missing part of the main installation files or they may have become corrupt.
You could always try installing the latest Windows Installer to your system,this usually eliminates most installation problems.
http://www.microsoft.com/downloads/d...displaylang=en
Really though,removing SH3 from your system is unacceptable,this cannot be allowed to continue!
Good luck.