Julio of 3DSpotlight has sent me notice that their "Windows XP Memory Tweak guide" has been updated, hey! its good, informative and well worth the read. Tweakers stand ready!
Blurb: Windows XP, much like its predecessor Windows 2000 offers superior Memory management to Windows Millennium Edition & earlier. That said, both also require more memory to run efficiently. This guide will take you through configuring your system for optimal use of your memory subsystem – both RAM & the Pagefile. NOTE – This guide is based on Windows XP Professional, although should Home Edition raise any differences they will be included in the future.