Article ID: 183506
When you try to download a file from the Internet, you may receive the following error message:
Internet Explorer could not download filename from Internet site. The downloaded file is not available. This could be due to your Security or Language Settings or because the server was unable to retrieve the requested file.
This issue can occur if the Index.dat file in the Temporary Internet Files folder or the Cookies folder has been marked with the Read Only attribute, or the Temporary Internet Files folder is too full.
To resolve this issue, follow these steps:
The Index.dat file may be marked as Read Only during an upgrade or when you install another program. The Index.dat file is a cache file that Internet Explorer uses.
For additional information about cache files, click the following article number to view the article in the Microsoft Knowledge Base:
178702When you download a file, Internet Explorer assigns the downloaded file a unique identification number and then searches the Index.dat file for that identification number. If the downloaded file's identification number is found, the contents of the file are stored locally on your computer's hard disk and Internet Explorer uses the locally stored content instead of downloading the information from the Internet. If the downloaded file's identification number is not found, the contents of the file must be downloaded from the Internet, and the Index.dat file is updated with the file's identification number. If the Index.dat file has the Read Only attribute, the file cannot be updated.
(http://support.microsoft.com/kb/178702/ )Description of the Mm256.dat and Mm2048.dat Files