You can get a linux version of realplayer that works with Slackware here :
http://forms.real.com/real/player/unix/unix.html
Just get the Linux 2.x (libc6 i386) version then follow the directions on the download page : Once you've successfully completed the download, you will be ready to install the RealPlayer. To do this, you must make the installer executable and then run it:
* Example:
chmod u+x rp8_linux20_libc6_i386_cs2.bin
./rp8_linux20_libc6_i386_cs2.bin
It works for me.............. Have fun
GrayGhost