Ignore the third link, it was for Vista only, and I linked it only to show the driver needed.
Since you have applied Microsoft's UAA patch, you now only need the XP driver:
Realtek's site appears to be a little slow, try this mirror for the driver:
http://www.majorgeeks.com/download4902.htmlCompletely unrelated: yes, you should consider installing SP3 and all Microsoft Updates in general on any computer you have on the internet.