From my own experience, where for a while I could only get 3 of the 4 banks to work, I'd say no.
My Win7 scores with memory with different combinations in the slots were;
1-512mb, 2-512mb 3-empty, 4-empty ... score = 4.4 (Dual)
1-1gb, 2-1gb, 3-empty, 4-empty ... score = 5.4 (Dual)
1-1gb, 2-1gb, 3-512mb, 4-empty ... score = 4.1 (Single)
Much better to be Dual.