I'm assuming this is possible in the applicationhost.config file but I did not see a parent paths setting.
How do you allow parent paths for a specific site running under IIS Express?
Browse to C:\Documents and Settings\$your user name$\My Documents\IISExpress\config
Open applicationHost.config
Find the <system.webServer>
section
Change the <asp>
section to the following…
By default it only had the cache and empty limits bits but feel free to adjust any parameters you don't want.
<asp
enableParentPaths="true"
bufferingOn="true"
errorsToNTLog="true"
appAllowDebugging="true"
appAllowClientDebug="true"
scriptErrorSentToBrowser="true">
<session allowSessionState="true" />
<cache diskTemplateCacheDirectory="%TEMP%\iisexpress\ASP Compiled Templates" />
<limits />
</asp>
Save and restart iis express.