I have just seen a PC on Ebay with three os installed... Vista Ultimate... Applemac's Tiger
And Linux abuntu. Is this possible and practicle and how would it be done... Thanks

installing multiple operating systems - Google Search

Lots to read there. Many use a boot loader such as GRUB: GNU GRUB - GNU Project - Free Software Foundation (FSF)

You also have to be very familiar with partitioning.

Thank you I'll have a look...

I too have been playing around with loading two OS on my laptop. It is not an easy task. But the boot loader GRUB is most recommended. If you achieve any success please tel me.