Can you give me more details about you Windows version and WireframeSketcher version that you are trying to install?
Sometimes the installation might not work with certain locations due to permission issues. In these situations you might need to run the installer under an Administrator account. Can you try with a different location, like c:\WireframeSketcher and see if it works? One way to check that the INSTDIR option is passed correctly is to remove the /S option and see if the correct directory shows in the installation wizard.
Once you have a working installation, create the wiresketch.key (make sure to place the entire key there with BEGIN and END delimiters) and restart the application. If the key doesn't work then please email me the log file as produced by Help > Report a Bug.