I'll add a link to the 80386 manual's section on page translation, which describes in more detail the multi-level page table structures that the article mentions.
Multi-level page tables were definitely a necessity in the early days of 32-bit computing, when a 4MB linear page table (required to map all of the 32-bit address space) was quite a lot of memory to ask for!
More detailed resources -
http://www.red-gate.com/community/books/under-the-hood-dotne... - Contrary to title, it is not dotnet specific
http://support.microsoft.com/kb/2160852?wa=wsignin1.0
http://members.shaw.ca/bsanders/WindowsGeneralWeb/RAMVirtual...