a windows boot disk is a floppy disk that when put in your computer when it is off and then, consequently turned on, will start a very simple windows. It is not like knoppix or any "live CD" but it avoids booting off the harddrive. It is used to start a windows install (from CD)... some people also use them to start a computer with CD Rom support while avoiding whatever is on the hard drive.. and then using whatever CD, it doesn't have to be the WIN98 cd.
As to partitioning and Mandrake:
It's not that hard. Just make sure that your windows is defragged (so all the data is lumped together) and check how much you are actually using on the hardrive (click My Computer rightclick the hardrive (C?) and click properties.
If you have the space (not using up all the space with data, not windows) then start the Mandrake install. It has a nice gui partioning tool, you should see your harddrive and it should have a rectangle representing the windows partion. Now right click on that rectangle and choose resize partion. Change the size so that you have reasonable room for linux.
Now: make a / partion and a swap partion. This is very easy and intuitive, so I won't explain it all. (plus I don't remember...
)
continue the install.
This should work... keep asking questions if it doesn't.
The piece of advice I would give to any person ready to start is:
Make sure you back up all your data, then just go for it. A reinstall doesn't hurt. much.
titanium_geek