Seriously, how much do you know about pc's?
Edit: Wait, you want to install Windows XP and don't know how to backup files on your own harddrive? Then would you even know HOW to install windows xp and its drivers.(Just asking, please answer and i'll probably assist... :P)
You need to backup atleast some files on another partition. And if you have no clue what i'm talking about, try finding a manual on the internet on how to create a partition. READ CAREFULLY OR YOU WILL DESTROY YOUR PC... in a matter of speaking.
I'm not that much of an expert myself, but atleast I managed to search and find what I needed instead of just asking here and waiting for answers.
srsly, had to say that. You ask too much and the wrong questions. There's alot of information on the internet that could help you answer questions like that by yourself. To start off you could start checking some geek sites on computers or maybe just google "Computing for dummies".
No offense, but we all have to start somewhere. And that somewhere is where you stop asking questions to people and start asking them too yourself on the internet.
Google is your best friend with this.
Goodluck, here's a little helpful link to get you started.
Partitioning Hard Drives in Windows XP