Must memory be added so that slots contain equal amounts?

I have a Toshiba Satellite Pro P200-1KE - Core 2 Duo T5550 1.83 GHz laptop. It's running Vista SP1 Business pretty adequately with the 2Gb RAM supplied, 1Gb in each of two memory slots. But not completely adequately. So I would like to add an extra 1Gb. I think adding 2Gb would be wasteful, as the system cannot make use of the full 4Gb. However, the manual seems to be telling me that I need to put the same amount of RAM in each slot (it is a little ambiguous - but that would be the safest interpretation). Even if that is what the manual is meant to be saying, is this nonsense? Can I have 2Gb RAM in one slot and 1GB RAM in the other? Or do they need to be balanced with the same amount of RAM in each? It would mean discarding and replacing two perfectly good memory sticks instead of just one - irritating.

 

Blimey O'Reilly Steve - it must be around 3:30 am in Texas - don't you ever go to sleep? But thank you for a rapid, succinct and useful response.