This error means uninstallation executable is running and is in use. It is located under your Windows directory. It is either uninst.exe or IsUninst.exe (depending on the InstallShield product that has been used to create the setup). Reboot the machine and
make sure no other application is running that will load this executable into memory and then run the setup
again. If it does not help then go to your Task Manager on your NT machine and see if the uninstallation file has been loaded into the memory. If so then end that process and then run the setup again.
Delete all instances of IsUninst.exe from the %systemroot% directory and run setup again.