memory managment under Windows XP

I am using R 2.2.1 in a Windowes XP environment.

I work with very large datasets, and occassionally run
out of memory.

I have modified my boot.ini file to use the "/3gb
switch".

I also run the following line after I launch R ( I am
unsure if it is helpful).

"memory.limit(size = 4095)"

Please point me to useful references on how to better
manage memory, or suggestother actions.