Earlier there was a post asking if Q2A works on IIS with PHP installed. There was a comment that read it works fine other than the url rewrite portion.
This works, but you have to create a custom web.config file for the directory where Q2A is installed. It pretty much mimics the code that the htacess file would have on an apache server.
Below is the web.config file that needs to be placed in your Q2A directory. Also make sure you have the first option selected for your url structure in your Q2A admin.
web.config
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<rewrite>
<rules>
<rule name="Question2Answer" stopProcessing="true">
<match url="." ignoreCase="false" />
<conditions logicalGrouping="MatchAll">
<add input="{URL}" pattern="^(.*)//(.*)$" ignoreCase="false" />
</conditions>
<action type="Redirect" url="{C:1}/{C:2}" redirectType="Permanent" />
</rule>
<rule name="Question2Answer2" stopProcessing="true">
<match url="^.*$" ignoreCase="false" />
<conditions logicalGrouping="MatchAll">
<add input="{REQUEST_FILENAME}" matchType="IsFile" ignoreCase="false" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" negate="true" />
</conditions>
<action type="Rewrite" url="index.php?qa-rewrite={R:0}&{QUERY_STRING}" appendQueryString="false" />
</rule>
</rules>
</rewrite>
</system.webServer>
</configuration>