Vista SP1 & Memory

I just thought that you all might like to know a little something that happened to me after I installed Vista SP1.  Short background, I ordered a XPS M1530 w/ 4Gb of RAM & Vista Ultimate (32-bit natch), after getting it yesterday, I started to install my software and the Windows Updates.  I downloaded the full SP1 from MS and installed it with no problems onto my system.  Naturally curious to see if it really had worked, and it did, I took a look at the information screen to see if it said "Vista Ultimate Service Pack 1" and to my surprise I found that my system now registered the full 4Gb instead of the 3.5Gb that it had before.

I am curious to know if anybody else has had this occur, especially since I don't recall having read that MS had updated the memory recognition for its 32-bit Vista OS when I had skimmed over the highlights of the SP1 update.