Install the following four things:
2a. Download the KernelEx file (I used 0.3.3e, not sure if future versions will work, though they probably with). File is at: http://www.msfn.org/board/KernelEx-v033e-released-t71476.html&st=900#entry757714 Follow the install instructions.
2b. Create the following file: C:\WINDOWS\KEXVER.INI and put in it
[PerApp] Firefox Setup 3.0 Beta 5.exe=win2000
Download and run the Fx3 (I used fx3b5) installer and do that.
Download Uberkern at http://www.msfn.org/board/UberKern-t115731.html&s=aa84bf6c93d9050d285b0590259625a8 and put the zip files in Fx3 folder. Then take the XUL.dll file and put it into the .exe that comes with Uberkern. It's say "Mabey Okay" or something like that, and it should be good.