If you are using the 32-bit nVidia GeForce 5 FX driver version 173.14.xx, you need the latest driver version 173.14.39 for Slackware 14.1.

According to nVidia's web site, version 173.14.39 is going to be the last release of that driver. No further releases are planned.

For future kernel or X-server releases you may have to use the nouveau driver or the generic Linux driver with no 3D support.

Here is a link to the driver. It is a bit hard to find on the nVidia site. Check your graphics card to make sure that it is supported by the driver.

Linux X86 Driver for GeForce 5 FX Series 173.14.39

here is the FTP nvidia driver page
-- 64 bit
ftp://download.nvidia.com/XFree86/Linux-x86_64/
ftp://download.nvidia.com/XFree86/Li..._64/173.14.39/
-- 32 bit
ftp://download.nvidia.com/XFree86/Linux-x86/
ftp://download.nvidia.com/XFree86/Linux-x86/173.14.39/

and the HTTP "unix driver page"
http://www.nvidia.com/object/unix.html