Does anyone know how to prevent this situation? On my old celeron 400mhz, running windows 2000 pro, I compile a file and my app runs fine. On my brand new P4 1.8ghz running XP. I compile the same file and it stops with a NMAKE: fatal error U1077 'c51' : Return code 0x3. And in the .LST file, at the end I have this C51 FATAL-ERROR - ACTION: ALLOCATING MEMORY ERROR: MEMORY SPACE EXHAUSTED C51 TERMINATED. Thanks, Roger