Steps to rebuild a computer:

1. Identify what software you have and make sure you have the installation media for it.

This Windows XP installation will completely erase your hard drive, including all data left on the C: drive and all applciations. Give me a list of whatever you are missing and let's see if I can get you a copy.

2. Identify what hardware you have on your system and download drivers for it.

What you want to do here is:

Browse to Start - Settings - Control Panel - System - Device Manager

You will pretty much want to write everything that appears in that list, especially video cards, sound cards and network cards. Save yourself a ton of grief and download the drivers for these devices first and burn them to a CD. Whe worst pain is to blow away your installatin to descover that your network card isn't auto detected by windows XP and you don't have a driver for it, and since you don't have a driver, you have no way of hetting onto the internet to get one. Massive headaches.

3. Write down your network settings.

- Click Start - Run
- Type cmd, hit enter
- When the DOS window appears, type in:

ipconfig /all <enter>

Write down: 
IP address
Gateway
Subnet Mask

DNS1
DNS2

I think you mentioned that you have a Linksys router, in which case all of these network setting are delivered to your computer automatically via DHCP. You'll know because the IP address will be something like 192.168.1.100, instead of a public IP address.

4. Back up your data.

Documents, quicken data, favorites, music, pr0n, whatever. Back it up. You think it's safe to move it to your D: drive and 90% of the time it is. But that tenth time when you are in a hurry and not really paying attention (or you just don't know what you are doing) you'll blow out the wrong partition and that shit is gone forever, baby.

Burn it to CD's DVDs, floppies, whatever. Just get it done. Plus you need a good backup strategy anyway, right? So you might as well start now.

Before backing up your data, run a full, thorough virus scan with the latest virus definitions. No sense backing up your data if it's lousy with viruses.

5. Take the plunge.

Install your Windows XP CD, reboot your computer and select the option to boot from CD. You'll be on your way. DO NOT upgrade from a previous windows version. Chose to do a fresh installation and chose to delete, recreate and reformat your C: drive (assuming your data is on your D: drive). This makes for a cleaner installation with fresh versions of everything.

The installation takes about 30 minutes, after which you will have a virgin version of XP that has hopefully detected your video card, network card and sound card.

If not, here's where you use the driver disk you made.

6. Harden your computer.

Make sure you run Windows Update as soon as you can yo harden your computer against malware.

You will also want to run anti spyware software, like Spybot S&D or Microsofts AntiSpyware Beta.
If you don't have antivirus software, use AVG's free version from grisoft.com. It's excellent and free.

7. Install software packages.

Install Office, Quicken, iTunes, whatever.

8. Restore your data.

Now's your chance to organize all your crap in meaningful folders like you've always meant to. Now is also when you start remembering all the stuff you meant to backup, now that it's gone forever.

9. Pat yourself on the back. You've just survived the most invasive and disruptive process you can do to a machine.

9a. Go drink. Heavily. This is a long, boring but stressful process. There's a reason why I get paid to do this stuff. People just don't want to be bothered with it but want new stuff.