The setup program for slackware is text based, but there are colors and it uses an easy to follow menu. Basically, pop in the cd, login as root, and type setup. Then you will be presented with a menu.
First select the target partition. It will scan for linux partitions on your drive. Just select the one you want to use for slackware.
I just want to know if i portion off 20 gig for slack then is it as easy as selecting the empty piece i made and installing it into that part of the hard drive
Yes, all you should have to do is just portion off a linux partition for slackware and it should work fine if you just select that from the setup program. I'm dual booting as well and all i did was split up my xp parition and make a swap and ext3 parition for slackware. Works fine.
Then after you do that, select your swap partition.
Then you will be presented with a menu of possible packages to install. I usually select all of them (except extra kde languages) (select things with spacebar).
After that, choose the install type. Full is the easiest. It will start to install everything automatically.
After it is done installing to the hd, it will then load a program to configure your system. Some things it will ask you are if you want to make a boot disk, and configuring which things start up.
Also, it will load a lilo configuration program. There is an option to install lilo automatically or use advanced mode so you can add operating systems to lilo yourself. After you finish configuring, it will take you back to the main menu. Just go to exit, reboot your system, and enjoy.