Hello,
Any inputs on the possibility of executing a shell script on unix box from Windows FTP
TIA

That should be impossible. Over the years, a few ftpd implementations had some problems that allowed this. But these problems have been fixed. With some co-operation, this is possible in a limited sense. A periodic cron job could check for newly arrived shell scripts and run them.

A better solution is to use a protocol intended to run stuff. Windows telnet is one solution. Telnet has some security problems, but that ftp idea is even worse from a security standpoint.

ssh is a still better idea... recent versions of ssh are very secure. You will need to download putty, but it's free. I run stuff on unix and linux system from XP all the time with putty.