Paul
I have followed your advice and removed FTN95 v 4.50 and installed the new FTN95 v5.10 on the VISTA machine. Unfortunately I still get the same Access Violation problem when I use the command line FTN95 TEST1.F/DEBUG/LGO If I leave out DEBUG all is well provided TEST1 has no errors. TEST1 is any simple program.
On the Access Violation box it says ' Exception C:\Program Files\SILVERFROST\FTN95\SDBG.EXE' In the box it says The instruction at address 100470a3 attempted to read from location 843809a4.
Martin