First, I would suggest you go to the CNET download site:
where you can download the Win4Lin install and obtain info
on requesting a trial license ($89.99 otherwise).
Patching your 2.4.20 kernal in Slackware (there are no
pre-enabled kernels for Slackware) is explained here:
Read carefully; you'll need both the kernel patch and the
After patching, you'll see an extra menu selection in 'make
Hope this helps.