First, you probably won't be able to find much/any help specific to IE7, as it hasn't officially been released. (No Microsoft help articles, little/no user experience, etc.) However, I'd suggest clicking here and following Microsoft's instructions for repairing or reinstalling Internet Explorer 6.0 and Outlook Express in Windows XP. It involves editing the registry, so make sure you back it up (go file->export in the registry editor) before proceeding. Hopefully the fact that IE7 is installed doesn't throw a monkey wrench into things.
Second, IE7 is only in Beta1 and lacks some of the major functionality that's promised to be included in the final version. At this time it's for developers only, followed by the Beta2 release to the general public sometime in the future. Thus, installing IE7 wouldn't give you much added functionality, wouldn't give you the full product, and is still buggy...not recommended for the standard user.
Finally, you mentioned ''media player 3...'' If you are talking about Windows Media Player, it is currently at version 10. I believe even the first realeased versions of XP included WM10, so I'm a little confused as to why you have a version that old. In any ase, I'd recommend upgrading by clicking here. (Note: Validation of legitimate installation is required.)
Hope this helps,
John
P.S. Don't post the location of the download, but let me know what your first impressions were. I've seen some screenshots but not much feedback.
this has been happening for a little while now. so what happens? well when i go into IE (in XP pro), it loads as per normal then it crashes as soon as it starts rendering the page. the problem is more than this - since microsoft has all these other apps that need html, like media player and help, they simply won't open. i decided to hang in there until the IE 7 came out, because wiping my computer is a big pain and i avoid it whenever possible. the day has come and i managed to find a leaked version of IE 7. it installed and thinking that this new installation would fix the problem, it still crashes. would anyone know a solution to this problem? (it's not so much IE that's the problem (i've gotten quite attached to firefox); watching video in media player 3 is plain drab!) any suggestions would be very much appreciated!

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