I am planning to install Slackware 9.1 on my computer which already has Win XP and Mandrake 10 Official. The idea is to put slackware in a 10Gb partition on my second HD. In order to do so, I have some questions and I will really appreciate your valuable and "detailed" help.

Note: Maybe some of the questions will sound trivial or obvious but take into account that I am almost new in linux and want to avoid some possible mistakes. Thanks for your cooperation.

Questions:

#1: Is it ok to create these three partitions: Swap, /root and /usr? How much space should I assign to each of them (in a 10Gbytes whole partition)?

#2: When installing Slackware and in order not to lose WinXP and/or Mandrake, How do I tell Slackware to install in the partition I want it to install? I think this will be asked during installation but I want to make sure.

#3: VERY IMPORTANT: Now I am using Lilo as my boot loader (installed by Mandrake). After installation, How do I add Slackware to Lilo so I would be able to choose among WinXP, Mandrake and Slackware?

#4: Any advice will be welcome.

Thanks again friends.

Prepare the partition you want to use first. Write down what it's called. The Slack installer will ask for it during the install process. You can use the same swap partition that Mandrake uses. I would just put / and /usr on the same partition. I don't see any advantage in making things more complicated. One time I had /usr on a 2Gb partition which I thought would be plenty but it filled up and I couldn't install anymore software. Copying the whole /usr folder onto a new partition was complicated. Since then I always install onto just the one partition for everything. 10Gb should be plenty.
I've read other people have been able to boot several versions of linux with lilo but I've never been able to do it. I would strongly recommend that you use the Mandrake Control Centre to change the boot loader to Grub. Then when you install Slack choose not to install lilo, add an item for Slack to the /boot/grub/menu.lst in Mandrake. This boots Slackware 9.1 for meGrub counts from 0 so all the numbers are one less than normal, also, it uses numbers not letters for the drive so for example, /dev/hdb3, the third partition on the second hard disk would be written (hd1,2) for grub.
/dev/hda7, the seventh partition on the first hard drive would be written (hd0,6)

Thanks Andrew Benton for your help!

I could install Slackware thanks to your answer. Very clear and very helpful.

Thanks again.

Well thankyou. Well done for getting it fixed and thanks for posting back.