URGENT! Localhost problem

Hi i need urgent help.

I was developing my first ever WP theme about 3-4 months ago from now, but due to some reasons i had to stop work on it.

In the meanwhile i installed IIS and Visual Studio to practice my ASP.Net projects.

Now, when i tried to continue building my theme, after 4 months, my Apache is not getting connected only through my Xampp control panel. It says:
WARNING: terminating worker thread 0

Upon research ( https://assethost01a.iterasi.net/ec2eb670e447/94d5ad32ba6b/ff6f9e86baa1/6a8a3ac75a10/56ed2c07-0a84-409c-9104-76a507c43be2/95a881d1-8f3b-4da3-834f-d52c4fbc112f-default.html???20110314173925???bJf2uf872+1/jEoodY+eGybnTIAvPW2Lrqs5j0hasZPBikqO7pCX+sndsx5bugQ9GQekcSYgveTKK4FPKoNqDkf4XdbTU0hqLgigZBphHcu1mMk4hSuri3Bk+voBKnmgqLgp19/Rr1JDpVEJP4e6csaS5MEZw0eOQ9ZOX23AuQY=#nostart ), i found that IIS and Apache both use port 80.

Now i want to know, how to get things working again? Is there a way to shift my apache to port 81? Or what else can be done?

Quoting from the link mentioned above:
” The apache does not start on my system!!!

This problem can be several reasons.
(1) You have started more then one HTTP Server (IIS, Sambar, ZEUS and so on). Only one Server can occupy port 80. So you must terminate one http server, before you start the Apache.”

Please help me ASAP. Thanks.

[sig moderated as per the Forum Rules]