For X session on PC, you can install Exceed form Hummingbird on your PC. After telnet into the UNIX box run the command "DISPLAY=pc_ip_address:0.0;export DISPLAY" if your are running ksh,sh or bash, "setenv DISPLAY pc_ip_address:0.0" for csh and tcsh. Then any X program will display on your PC.
Like CUViper say, It's better to tunnel X with ssh but you still need exceed.
Joe