My question is about Internet Explorer 8 Beta Why ...

I really do not know, Why should you go with Internet Explorer beta vertion?

It is still under construction. You should get another web browser.

There are lots of browser avaliable like:

> Mozilla Firefox

> Opera

> Google Chrome

If you want more browser help please approch at:

http://www.iyogi.net/internet-browser.html

SP3 has a newer time stamp on files  than the IE8 Beta.

Windows prevents installation of older files.

Try to uninstall SP3, Install IE8 and than reinstall SP3 and hope it would not harm the IE8. 

why can not i install internet explorer8 in my windows xp?

It is quiet a natural thing to happen because the version of IE that you have is newer than the version you are trying to install and Windows prevents this. Tell me one thing that -does it really matter which browser you are using? Are you not just wasting your time upon an unnecessary thing? If you are too much inclined upon installing IE8 beta then uninstall your present Windows XP SP3 and install a previous version and then try reinstalling your beloved IE8 beta. By the way I use Firefox and I'm satisfied - you too can download it for free from Google. Anyway if you want to take your mind off this mess and want to know some cool ways to make money online then visit my blog titled - Make Money Online .

This will be help you

http://www.terryscomputertips.com/computers/installing-windows-xp-sp3-and-ie-8.php

For more details Please visit www.iyogi.net