General Description: I wish to install 4.1i and keep 3.1i on the same system, and I would like to access them both by changing the $xilinx environment variable manually to switch between versions. However, after installing 4.1i on a system where 3.1i is already installed and switching back to a 3.1i version, the following error is reported during implementation:
ERROR: NGDBuild:205: Undefined keyword "Quit" in option string.
This can occur if the Project Navigator Desktop icon is used to launch tools after you have changed the $xilinx variable to the previous version. The desktop icon points to the directory for 4.1i after the latest install, so the tools will not launch correctly after changing the $xilinx environment variable to 3.1i.
Generally, launching Project Navigator using the program group at Start -> Programs -> <your system's Xilinx> will launch the tools properly.
On some PC systems, you may need to reboot the system after changing the environment variable, and verify after reboot that your $xilinx variable is set to your 3.1i directory.
If you are still having difficulty with an existing 3.1i design, you may be able to implement it with Design Manager as a temporary workaround.