If you want to install IE7 without validation, read this tuto.
First download the IE7 setup.
Now you need two apps, the WinRar and the free XVI32 Hex editor.
If you try to install the IE7 you will get this screen:
To bypass this screen, unrar the IE7 file you downloaded. Then in the (unrared) folder, you can see another folder named "update".
Open the file iecustom.dll located in the UPDATE folder using XVI32
In XVI32 click on Search -> Find and search for the Hex string "0F 95" (zero f nine five)
Change the "95" to "94" and then click on File -> Save . Go to the UPDATE folder again and run the file named Update.EXE
How To Install Internet Explorer 7 beta 3
To install the latest beta (3) you must use this tool to change your product key to another working key (you have to search for working keys).
*NOTE: DO NOT RESTART THE COMPUTER AFTER CHANGING THE KEY!
Now go to "Update" folder and run update.exe