XAMPP stand of X(any operating systems), Apache, MySQL, PHP and Perl.
Generally, two servers cannot be run in the same with the same port.
Normally, web servers use port 80 as their default. Probally, XAMPP has
used port 80 since you installed. Then you installed IIS websever which
also defaultly use port 80. So you should assign different port for each
webserver. As what chrishirst have been mentioned above.

From siLenTz
Sleepy... It is 3:30am here Can't sleep...

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