You are trying to convert a movie into a still picture. I don't think that's posible unless you freeze the frames. Check the Manual. bon chance ==============Original message text=============== On Fri, 07 Jul 2006 13:03:07 EDT "karamyog singh" wrote: Dear Users, When I try and convert my traj.xtc file to a .gro file I get the following error Reading frame 0 time 0.000 Precision of traj.xtc is inf (nm) Using output precision of 0.001 (nm) Fatal error: DEATH HORROR prec () <= 0 in prec2ndec Can anyone tell me what is meant by it? Thanks, Karamyog Undergraduate student, IIT kharagpur. ===========End of original message text===========