Ok I am going to try debian and I already have Slackware and I would like to know if during the install I can just format what it is on and I also have windows xp and I want to keep it. I read that install guide and did not completely understand it would format and already linux partition.

Never mind I kept reading and I don't think I can do all this.

Yes you can. Just point the Debian installer at your existing Linux partitions and tell the bootloader to overwrite what is already there.

The new Sarge installer (still beta) is probably the easiest way to install Debian. I have to admit that Debian is not the easiest distro out there but if you've already successfully installed Slackware, you might succeed also with Debian. Perhaps you should give the new installer a try before you decide that Debian is too difficult?

http://www.debian.org/devel/debian-installer/

Before you start messing with Linux bootloaders and MBR, you should always make a boot diskette for WinXP so that you can restore the Windows boot sector if anything goes wrong. Unfortunately Microsoft hasn't made this easy. You can create a WinXP boot diskette following the instructions given here:

http://www.xxcopy.com/xxcopy33.htm