Vista RAM Question

Recently I upgraded the RAM on my bigger Toshiba laptop to a blistering 4 Gigs from the stock 2 Gigs. Everything runs great, and surprisingly, even my dial up seems faster D: But theres something I gotta know. In both PC Wizard and in the BIOS, it says the memory controller can only handle 3 Gigs of RAM, but in the properties of the laptop, it still shows the 4 Gigs (PC Wizard shows 4, BIOS shows 3). So the question is, would it be fine to just leave the extra Gig in, or should I put back one of the 1 Gig sticks?

Thanks a-@