Quote - You shouldn't need the 3GB switch to get it seen by Windows XP Pro SP2 - it already supports it and I see 3GB without any switch on my system.  But it is a dual Xeon, so it may be required for a single cpu system (shrug).

The /3GB thing is not about how much physical RAM Windows can see. It is about how much virtual address space it will hand out to applications (that is, even on a system with 1GB RAM it can make a difference). See http://blogs.msdn.com/oldnewthing/archive/2004/08/22/218527.aspx for juicy details and mythbusting.