From the SolidWorks KB:
S-062141: How is the error "An activation prerequisite is missing, please reinstall (68)" when running the SOLIDWORKS® Activation Wizard resolved?
1. Open a command prompt (Start > Run > type cmd and hit enter)
2. Type 'cd c:\program files\solidworks corp\solidworks\setup\i386' to change to the <SolidWorks install directory>\setup\i386 folder If SolidWorks is not installed in the default location update the path as necessary
3. Type swlicservinst.exe -swip swx and hit enter
4. Type swinstactsvc.exe -swip swx and hit enter
5. Start SolidWorks.