execute shell file on DOS prompt

I have installed cygwin on my computer having windows 2003 server as operating system.

The following command works fine on DOS console:

bash launch_update.sh

Is there any way, that i could run the above shell file, just by typing its name on DOS prompt, in the same way as batch files are executed.

Nope. The one is a DOS/Windows prompt and the other thing starts a UNIX Bash Shell which starts the shell script. Maybe you can write a batch file like "launch_update.bat" which contains "bash launch_update.bat", if you like that more.