How do I run any X windows application

^^^^^^^^^ Please, say it as "X Window" :-)

Netscape on the remote machine to which I am connected by TELNET?

Start X on you local computer. Then start a xterm/rxvt session. In that give the command `xhost +remotehostname' eg.,

[user@lchost user]$ xhost +rm.lan.net

Then in the telnet session, start netscape like this -

[someuser@rm someuser]$netscape -display lchost.lan.net

You should be seeing Netscape in your X session, now.

Although, this is the easiest way to do this it is also the least secure. For further info, please read the Remote-X-Apps mini-HOWTO

HTH :-)

Fart