I am not very proficient at computers and want to learn how to use Ubuntu
since I read somewhere that it is the most user-friendly version of Linux.

I am not sure how to go about this but here I go -

I have Xandros installed on my machine but I want to remove it and
instally Ubuntu since I have been unsuccessful in learning how to use
Xandros. I have no idea as to how this is to be done.

My machine is a P4 2.0 1.0GB RAM WinXP Pro SP2 (alongwith Xandros which I
recently installed with kind help from someone). My 4 Windows partitions
are C:, E:, F: and G: and total size of G: used to be 51.2GB (55GB) but
after installing Xandros it is now 29.0GB.

Will this 29.0GB stay the same after removing Xandros and installing
Ubuntu or will the free space reduce further? Since I want to continue
using my WinXP till I learn how to use Ubuntu properly, I dont want to
lose any data from my Window's G: partition.

I would be grateful if instructions/help for the below are given in simple
terms since I am not good at computers (and totally zero in Linux!) -

1)How to remove/uninstall Xandros, and
2)How to install Ubuntu. (I have got a Ubuntu 7.10 CD from my monthly
computer magazine).