I just installed Mandrake Linux 8.0 about a week ago and I'm a complete newbie. My Microsoft Intellimouse explorer works as a two button mouse in Xwindows, but I want to use all 4 buttons and the wheel. Can somebody tell me how to do this? Thanks.

Not sure about this but the easiest way for a newbie I can think of is to try "Xconfigurator" at the command line and see whether there is an option for MS Intellimouse Explorer.

Else, you will have to edit your /etc/X11/XF86Config-4. The appropriate entry to edit under the "pointers" section can be found at http://www.xfree86.org/4.0.2/mouse6.html#27

HTH

Ok, I got the right pointers, and the mouse seems to work as a 3 buton mouse, but how do I get the wheel to work and set the other buttons for what I want them to do? I want one of the side buttons to be double-click and one of them to be back (like in a browser). Is this even possible?

Well, in order to get the scroll button working you are most likely going to have to edit /etc/X11/XF86Config by hand.
Find the mouse section and add:
"ZAxisMapping" "4 5" at the end of the mouse section, that SHOULD get the scrolling working. and it is type sensitive

Oh yea, one other thing X tends to screw up-if what i told you doesnt work, edit the file again and change the mouse type to "IMPS/2" , intellimouse doesnt work sometimes

Using RedHat 9, so I don't know if this works in Gentoo 1.4, but you may try it to get some functionality you don't now have.

In console type
setup
then choose mouse configuration and select the Microsoft - Intellimouse (USB). In RH9 this gives you three button mouse function, though the 2 buttons on the side have different functions than in Windoze. The front button on the side gives you a menu for the current screen, and the back button on the side tries to load a browser, though I don't know where it gets the address from. I am still trying to find out how to configure the buttons as I wish. There are settings in Mouse, under Control Panel, but there is no mention of the buttons.