Please advise how to open file with the .dat extension.Thanks

They are not meant to be opened by a user. If you insist, try notepad but you'll probably get a bunch of garbage.

You didn't give a context, so this could have been easier. Many e-mail systems send a *.dat file along with some e-mails, and they merely have tracer information for the e-mail you're looking at. Of course, if it's not attached to an e-mail..... Cheers! Chase

Hep is right. They are usually files that are specific to a program. If you got a .dat file through e-mail, you can convert it if you know what it was that was sent. When my wife sends attachments to me from work, they are always mysteriously converted to .dat files. She just lets me know what the extention was. If you know it's a picture, try, .jpg , .bmp , .gif . If it's a movie, try, .avi , .mpeg , or .mov . I'm just assuming here that this is what you are talking about. If it is a file you found on your harddrive, it will most likely be unreadable as Hep has already stated.

I had a problem with emails with DAT extensions. renaming it didn't work in my case. But if I opened netscape browser and dragged and dropped it into the browser window it opened/extracted the files. TheGorx Windows Help

Index.dat files are in 2 places on your hard drive. Microsoft uses these to log every website/banner/cookie on your harddrive. Some consider it a security/privacy issue as it uploads everything you do to Microsoft. They are intentionally tamper resistant. Microsoft does not intend to allow users to protect their own privacy. I have a program called Spider.exe that opens and cleans these files but will not open other .dat files. I got mine from download.com by searching for spider.exe security. Here is an excerp from the bottom of the opening window of the application: >>"If you find any bugs in the program, please contact Ward@Ward.nu Check out http://www.fsm.nl/ward for the latest information on this topic. Ward"<<