I have a windows XP SP2 IBM laptop with plenty of memory (512MB RAM) and processing speed. When I try to model a protein domain of about 750 residues (with a multiple alignment of only two sequences, the target and the strucutre sequence), the program runs for about 20-30 seconds and then I get this error: C:\Program Files\Modeller7v7\examples\tutorial-model>mod7v7 Toms-Initial forrtl: severe (170): Program Exception - stack overflow Image PC Routine Line Source mod7v7.exe 00507271 Unknown Unknown Unknown mod7v7.exe 004FEA3E Unknown Unknown Unknown mod7v7.exe 004589DE Unknown Unknown Unknown mod7v7.exe 0040653E Unknown Unknown Unknown mod7v7.exe 0040F5BB Unknown Unknown Unknown mod7v7.exe 006A564B Unknown Unknown Unknown mod7v7.exe 006EDB39 Unknown Unknown Unknown mod7v7.exe 006DC824 Unknown Unknown Unknown kernel32.dll 7C816D4F Unknown Unknown Unknown I've done all that is in my power to bump the memory management on my laptop, changing the virtual memory and paging sizes (to max). Editing the CONFIG.NT to explicitly stating number of stacks and stack size, etc. Nothing works! It seems that my computer should be able to handle modeller, no? Would you have any suggestions as to what may be going on and how to handle this? Also, I worked through the tutorial and it runs fine with the example files. Thanks for your help, All the best Tom Petty ----------------------------------- Graduate Student Genomics and Computational Biology Biomedical Graduate Studies University of Pennsylvania