Working for a CMS software development company one thing that we discovered when Windows Server 2003 was released was that when our clients attempted to upload media to our product, it was a bit hit and miss at times. What we discovered was a security precaution in IIS 6 limited the maximum file size that was up-loadable to 240Kb.
To resolve this issue, we increased the Maximum ASP upload by running the following from the command line:

	cscript C:inetpubadminscriptsadsutil.vbs set w3svc/ASPMaxRequestEntityAllowed 10484880

The example above updates the metabase.xml file and sets the maximum up-loadable value to 10Mb. This can also be achieve by opening the Metabase file (path below) in a text editor,

%systemroot$/system32/inetsrv/metabase.xml

Finding the ASPMaxRequestEntityAllowed node, and changing the value.

With Windows Vista and Windows Server 2008, the way to set this changed again! To achieve the same setting, it can now be done via the IIS Administrative tool. To change do the following:

• Open IIS Manager from the Administrative Tools
• Select the Server from the tree structure on the left hand side
• Double click on ASP in the right pane.
• You will see a list of properties, Expand the Limits Properties and you will see Maximum Request Entity Body Limit. Set the value here in bytes to the upload limit you wish to set. Click Apply.
• 

There is a similar limit imposed in all flavours of ASP.net. This can be configured in the machine.config file of the machine or in the web.config for the application. Adding the following under the <system.web> tag in the will increase the ASP.net maximum upload to 10Mb in this example.

<system.web>
      <httpRuntime maxRequestLength="102400" />
</system.web>

As you can see, it isn't too difficult to resolve this issue, although the way to change the setting can be difficult at first to find.
I hope this guide makes it a little easier for you.