From the simmarket web site
OK, then... let's try again. I want you to uninstall the application completely and delete any folder(s) and remaining files that might be left over afterwards. Then I want you to turn UAC off - if you don't already know how to do so, click on the desktop where there's no icon and then press F1, when help comes up type in UAC and search - open the first item and it will tell you how. Once it is set off you must reboot your computer. When that is complete, right click the FSB installer and choose "run as administrator" and then chose a location for FSB that is under the c:\ root in a place all its own. Do not install it in the "Program Files (x86)" subdirectory - this is important
. When that is done, run FSB from the right click "run as administrator", let it come up, close it, and look at the fsbuild2.cfg file - if it still shows the bogus s:\ whatever stuff delete it and run FSB again, close it, and then see if a new one was created. I know this is a pain but it has solved similar problems for other folks.