uninstall temporary os and install new os

[Chris]

I am not computer literate and need alot of help here - in layman's terms
please!

I bought a Toshiba that has a temporary 2007 operating system that has
expired. I would like to uninstall this and install a windows xp home edition
(I have the cd).

Is it as easy as going to 'uninstall programs', and then inserting the cd
and installing the xp edition.

I'm really nervous about doing this, but people want to charge me $75 and up
to do it for me, telling me that it is too difficult for anyone but a
computer tech. I am nervous about messing up and it costing me alot to repair
the damage I've done.

Can some one out there help me please? Thanks.