First of all I'm running Slackware 8.1 (xfree86 4.2.0).

I'm trying to install a S3 Twister K with hotkey graphics card. I know the driver for this is the savage driver, but it still won't work. In xfree86 4.2.0 it tells me the card is null, and I can only startx X by copying xf86config-fbdev to XF86Config, cheers.

how are you configuring your X windows? xf86config? xf86cfg?
post your file..

As root, try this:

XFree86 -configure

This will probe your hardware, and then go on to set up a basic XF86Config file in /root/XF86Config.new. It will then tell you that to test it,
you do:

XFree86 -xf86config /root/XF86Config.new

If that works, you can copy XF86Config.new to your /etc/X11/XF86Config,
edit it for more specific options, and go from there.
If it works, it will just bring up a grey screen with a mouse cursor in the
shape of an X, there will be no fancy anything, this is just the X server,
the window manager is setup later.

I can't run X -configure, it gives me the message that a valid card configuration was found, but hasn't been added to XFreePciInfo.h yet. I know that is uses the savage4 driver though and has chipset id 8d02 if thats any help.

Please post the XF86Config file that you are trying to use (please remove
all the comments so we only see what is actually being used). We don't
need to see the XF86Config-fb file. . .

Are you sure you are using the right driver name? From
http://www.xfree86.org/4.2.0/Status28.html#28

it says:

4.2.0:
.
.
.
Support (accelerated) for the Savage3D, Savage3D/MV, Savage4,
Savage2000, and SuperSavage, is provided by the "savage" driver.
Support for the other S3 chipsets has not yet been ported.

Maybe try :
Driver "savage"
as your driver line. . .

I have the twister k in my laptop running just fine... use the savage 3d driver. If you dont like it, then go to the s3 webpage and download the driver for linux.