Symptoms
When uploading images through the admin site, an "Access is denied" error is encountered.
Cause
The user account that the software uses to upload those images does not have sufficient access to save images to that folder.
Solution
Grant the .NET user account (typically ASPNET for WindowsXP or NETWORK SERVICE for Windows Server 2003/Vista or IIS_IUSRS for Windows Server 2008/Windows7) Read/Write/Modify access to the /Images folder.