Change group/owner of dir or files

Hi all, Thanks for all the help I have received from this group. I have tried to change group owneras root, but in all cases it says "operation not permitted" To be be more specific I have a DOS partition where I have installed dos OS and a Dos programm, automaticly this partition is mounted at start up of Linux in /home/dos, but as mentioned before I can not change the group or owner. Only when I login as root on a win95/98 machine it is allowed to execute this dos programm installed on the Linux server. Does anyone know what I'am doing wrong here. Thanks for any suggestions, solutions. rgd Wil