[waynf]

Could someone please give me in lay-man terms definitions for Prefetch Data and Index Dat files and their relationship to one another if any.

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There is no relationship between them. The purpose of each is quite different.

This is Microsoft's own explanation of the purpose of prefetching data:

"Windows XP monitors the files that are used when the computer starts and when you start applications. By monitoring these files, Windows XP can prefetch them. Prefetching data is the process whereby data that is expected to be requested is read ahead into the cache. Prefetching boot files and applications decreases the time needed to start Windows XP and start applications".

I would also add that contrary to advice given on several websites, clearing out the prefetch folder does not improve performance. On the contrary, doing so can adversely affect performance. I only remove from the prefetch folder those applications which I've uninstalled, since their prefetch data is redundant.

'index.dat' files are created and updated by Internet Explorer and are essentially a database of all the websites you've visited and related cookies. There are several index.dat files on your system. It's important to realise that even if you delete your browsing history from within IE, the index.dat files are not touched. But it is possible to delete them when Windows restarts by using a free cleanup utility such as 'Ccleaner'. When they are deleted in this way, Windows just creates new ones but they contain no data until after another browsing session.
See this: http://www.exits.ro/...-dat-files.html

Edited by pip22, 15 April 2008 - 12:45 PM.

[pip22]

There is no relationship between them. The purpose of each is quite different.

This is Microsoft's own explanation of the purpose of prefetching data:

"Windows XP monitors the files that are used when the computer starts and when you start applications. By monitoring these files, Windows XP can prefetch them. Prefetching data is the process whereby data that is expected to be requested is read ahead into the cache. Prefetching boot files and applications decreases the time needed to start Windows XP and start applications".

I would also add that contrary to advice given on several websites, clearing out the prefetch folder does not improve performance. On the contrary, doing so can adversely affect performance. I only remove from the prefetch folder those applications which I've uninstalled, since their prefetch data is redundant.

'index.dat' files are created and updated by Internet Explorer and are essentially a database of all the websites you've visited and related cookies. There are several index.dat files on your system. It's important to realise that even if you delete your browsing history from within IE, the index.dat files are not touched. But it is possible to delete them when Windows restarts by using a free cleanup utility such as 'Ccleaner'. When they are deleted in this way, Windows just creates new ones but they contain no data until after another browsing session.
See this: http://www.exits.ro/...-dat-files.html

Edited by pip22, 15 April 2008 - 12:45 PM.

[waynf]

When you say that Windows just creates new ones, do you mean it adds them as you browse more sites or does it merely drag them out of the registry.

The reason I am interested in this area of operation is that I have scanned about 900 photos and saved them on my files in efforts to compile a family history profile. Could this plug up the registry even though they are saved to disc and deleted in the normal process of "delete". Maybe this is a different question altogether, or are the the index.dat merely history data of sites visited.

I downloaded an application that shows you your dat.files from the link on your last response, and here is a case in point. Last night I ran a CCleaner, Also cleaned the disk using My Computer?Properties?Disk Cleanup. This morning I turned on computer, selected Index.dat File Viewer and there were several entries, even though I had not logged on to internet yet or did any browsing at all.