fix computer errors

I have a Foxpro DOS based programme for billing software, it is a multi users. Now My server is Windows NT4, My Nodes are having Windows 95, Windows 98 and Windows XP. Now when I run the application in DOS mode from the PC where the Windows 95 OS is loaded it runs without error and lets all other Nodes to run smoothly, BUT if I close that PC which is a 486 with Win 95 OS and try and run from Windows XP OS then there is an Error stating ” Source Not Found” and “Too Many Files Open” and then either I hv to say ignore,ignore and go back. But If I cancel then it does not give to close/quit Foxpro. I have to close from task manager, I have even set config.sys the files and buffers same as WIn 95 OS. But still same problem. Can Any one help me how to resolve it.