Hi Husk!
Like I promised in an other topic I'll tell you what you want to know about formating a PC...
Basically the description you found is correct - but before you start you should save all your important files you have, because everything which is stored on the HDD/partition is going to be deleted! :
How to Format a Computer with Windows XP
1. To format a computer with Windows XP or 2000, insert Windows CD and restart your computer.
2. Your computer should automatically boot from the CD to the Windows Setup Main Menu.
3. At the Welcome to Setup page, press ENTER.
4. Press F8 to accept the Windows XP Licensing Agreement.
5. If an existing Windows XP installation is detected, you are prompted to repair it. To bypass the repair, press ESC.
6. Use the ARROW keys to select the partition or the unpartitioned space where you want to create a new partition. Press D to delete an existing partition, or press C to create a new partition.
7. Type the size in megabytes (MB) that you want to use for the new partition, and then press ENTER, or just press ENTER to create the partition with the maximum size.
8. Select the format option that you want to use for the partition (Recommended: NTFS), and then press ENTER.
9. After the Windows Setup program formats the partition, follow the instructions that appear on the screen to continue installing Windows.
To answer your questions:
But, Whats a partition? And how much MB should I have?
A partition is a part of your HDD - you can separate it into more parts...
for you it probably is the easiest and best way only to use one partition - that means that if you get asked how big the partition should be while setting up windows, you should choose the whole possible space.
or which is more probable is that there is already one existing partition (probably C:) which only needs to be formatted
that means for you: if you get to the window where windows wants to know where you want to install it, there will be at least one entry where you can install windows (mostly the first entry in the list is the partition where already is Windows installed) - so you choose that one and format it --> then install windows on this partition...
The partition where windows is going to be installed should be not too small! at least 10 GB (if possible) because basically every program is installed on this partition and also the 'swap files' and the 'private files' are stored there...
i know this is difficult (also because I'm a bad guide...

) but if i was you i would just try to enter the windows CD and try to go to that window just to see which entry's are there... (which options) - but take care, that you don't delete the whole system

if you need more help just ask
yours
onlysomeone