Question : Problem: 512mb PC2700 + 256mb PC2100

I want to upgrade a Toshiba Satellite A40 (2.6ghz celeron cpu) laptop running XP Home.  
It currently has 256mb PC2100 ram installed in 1 of 2 slots, and I plan on adding 512mb PC2700 ram.  
I realize that even though I'm installing faster ram, it will run at the slower ram speed, unless I install it by itself.
So, with this type of system, would I be better off running the COMBINED ram (768mb) at the slower speed, or running ONLY the 512mb at the faster speed?

Answer : Problem: 512mb PC2700 + 256mb PC2100

I cant see you seeing the deference. And more is better.