Hi.Problems with my windows XP.

Hi.I just found this forum and its like made for me because im a beginner , (or not even that) in computers.i got 3 issues that i need everybody that can to work on.

1st issue
I do not know how to format my computer , i have been searching google for formatting guides but with no success yet.

2nd issue
I do not know how to delete my windows xp to re-install a fresh copy of it and yes, again, i have been searching through google for this problem too.

3rd issue
When i start my computer , past the ASUS logo , i get this:
Please choose the OS to start (or something like this)
Windows XP Professional
Windows XP Professional
Windows XP Setup

And i dont know how to get that setup out of there , i think its there because i quitted a setup before it was finished.

System specs:
INTEL E8400 CORE2D 3.0GHZ Processor
500Gb memory
4Gb RAM
nVidia 9600 GT Graphics Card

Please help me! Sorry for any typos and thanks in advance!