I have been fighting with FSDS 3.51 for some time. I have installed it on Win7 64 bit with a 2 TB drive. It starts and I can set the paths to the compilers (XToMDL, or MakeMDL and BGLComp) but I get this error. I tried the help file and discovered the link to Abacus is broken. Is Abacus defunct? When I first tried to do the test compile recommended in the product sthe error was "cannot find the path to the Projects folder" - but the path displayed in the error message was correct. I fixed that by establishing a new subdir in my C: drive C:\FSDS_Proj and pointed the app to it. Now I get this message. I'm no PC novice but this confounds me. I saw the thread at http://www.sim-outhouse.com/sohforums that proposed changing Win7 registry entries but it also said that was not needed for v 3.51. Does anyone have any insights about this --- or a link to Abacus?