Where’s my RAM?

I bought (awhile ago)

Crucial 1GB 184-Pin DDR SDRAM DDR 400 (PC 3200) CT12864Z40B – OEM

That plus the

mushkin 1GB (2 x 512MB) 184-Pin DDR SDRAM DDR 400 (PC 3200) Dual Channel

Should be 2GB, but I’m only getting 1.5GB.

This is on my Asus A8N SLI Deluxe mobo.

The important part of the manual is:

I have the modules installed like so:

A1 A2 B1 B2
M  E   M  C

Where M=Mushkin, E=empty, C=Crucial.

How should I arrange this so I get all 2GB?