M$ knowledge base Article 555223
All processes running under 32 bit Windows gets virtual memory addresses going from 0 to 4,294,967,295 (2*32-1 = 4 GB), no matter how much RAM is actually installed on the computer. When RAM is in short supply (e.g. Committed Bytes is greater than installed RAM), the operating system will attempt to keep a certain fraction of installed RAM available for immediate use by copying virtual memory pages that are not in active use to the pagefile.
I also remember that a Win 32 box with 4GB of RAM will reserve .5 GB for itself.
w/e I haven't used Windoze in a long time. Don't remember it all now.