This is odd, Widows 7 64 only uses 1500 of my RAM installed and have 4500 left to play with. Never seen my RAM usages hit over 2500 when installing softwares. Could be the type of RAM you are using, the Cas Latency of the RAM, or the number of programs you are running at the same time.
You should also look into loneeagle's suggestion as well.