#1: A dual-boot system is relatively easy to configure. A triple-boot system is not. Do NOT attempt to configure a triple-boot system unless you are absolutely certain you know exactly what you are doing.

#2: Do NOT delete stuff if you don't know what it is/what it does. It is probably vital and its absence will bugger everything.

#3: You cannot have more than four primary partitions on a single hard disk. Try it and nothing will work. You will then have to do a lot of messing about before you can get anything to work again, if it does at all.

#4: Do NOT mess around with the Master Boot Record, GRUB etc unless you are absolutely certain you know exactly what you are doing. You will bugger your computer.

#5: Always back up your data. This goes without saying, but people don't and if you're going to mess around with the essentials of your computer you may very well lose something along the way - so make sure you don't risk anything you don't mind losing.

#6: Windows Vista is next to useless. If you want to install a multi-boot to test out Vista, just don't bother. It's not worth it and you'll save yourself days and avoid the possibility of bricking your computer, or bricking your other OSs and being left with Vista alone, which you will then discover is shite.

#7: Yes, you CAN make a triple-boot system with XP, Vista and Linux and maintain everything in working order, but for the love of G-d, DON'T.