At the DOS prompt try typing 'set' and check if the 'c:\program files\informix\bin' is set. if not you could enter the above via "start - Settings - Control Panel - System - Advanced (tab) - Environment Variables" this is for a W2000 environment. Oh, the autoexec.bat mod mentioned above requires a reboot. Oh anther thing, was the client install of Informix installed in 'c:\program files\informix' or somewhere else?
Cheers.