If your computer you are going to use has Vista or Windows 7 on it, let me know as the instructions will be a bit different.
Just about the time I stopped using XP I ran into a neat tool that will do all the heavy lifting of slipstreaming SP3 into XP and it will also do all the current updates as well.
First you need to get all the updates.
Create a folder called XPSP3 and then in there create another folder called updates. Download and unzip UDC
into this folder. Then run the batch file. This will download all the post SP3 updates.
Next create another folder with SP3 as the name. Then download the offline installer for SP3 here
The rest of the instructions you will need are here
. There are links to the next page along the top.
I would read thru everything and see if you have any questions. Also I would create a full XP SP3 disc with all components and no other drivers or programs. That way it will not matter if you ever have to change hardware and then need to reinstall windows.
Let me know if you have any questions.