The default allowed file size for upload in IIS 6 is rather small, which is obviously not particularly good when it comes to a site with some or other upload functionality. Thankfully though, changing this default setting doesn’t require that much efforts, though you will need administrative access to the web server in question.
The steps are:
1. Open up the Internet Information Services Manager (IIS).
2. Right-click on the top level server and choose ‘Properties’.
3. On the resulting dialog, locate and tick the ‘Enable Direct Metabase Edit’ checkbox. (This allows you to make changes to the IIS metadata file without having to shutdown or restart IIS).
4. Locate your MetaBase.xml file: %Windows_Dir%System32InetsrvMetaBase.xml (Make sure to make a copy of this file for just in case!)
5. Find the AspMaxRequestEntityAllowed attribute in the XML file and change its value to the desired maximum file upload size that you want to employ (note that the value is stored in bytes so you’ll need to do the necessary calculations using good old 1024).
6. Save the MetaBase.xml file and that’s it, you;re done. There is no need to reboot the server or restart IIS.
7. Though just to protect yourself, go back to step 3 and uncheck the “Enable Direct Metabase Edit” box on your IIS server properties’ page.