after installing microsoft web-matrix if your xampp control pannel show that system is using port 80
and you are unable to start xampp control pannel
then here is two methods you can get working xampp installation

1 : disabling web-matrix web deployment service
Steps : 

• click on start and search for ‘services’

• open services 
• look for ‘web deployment agent service’

• stop that services or change properties to manual 
• restart xamp 

• done !

2 : changing Apache Listening port (recommended)
Steps 

<li>
  <span style="font-family: 'Trebuchet MS', sans-serif;">open apache configuration file ( httpd.conf ) &nbsp;</span>
</li>
<li>
  <span style="font-family: 'Trebuchet MS', sans-serif;">open with notepad&nbsp;</span>
</li>
<li>
  <span style="font-family: 'Trebuchet MS', sans-serif;">find &#8216; listen &#8216;<a href="http://4.bp.blogspot.com/-8seGlnLFMkQ/T4hjUBjKVaI/AAAAAAAACRs/e4q-9dBCe2A/s1600/search_listen.png" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-right: 1em; text-align: center;"><img border="0" height="418" src="http://4.bp.blogspot.com/-8seGlnLFMkQ/T4hjUBjKVaI/AAAAAAAACRs/e4q-9dBCe2A/s640/search_listen.png" width="640" /></a></span>
</li>
<li>
  <span style="font-family: 'Trebuchet MS', sans-serif;">change port 88&nbsp;</span>
</li>

• use http://localhost:88

• done 

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