Windows 7: memory goes up to 98% when installing any game. help..

Hy guys, after i installed the 7100 build i noticed something that didn`t happened before on earlier builds.
Whenever i install any game on my machine, my RAM memory goes up to 90%-98%.
I have 4gigs of ram so i don`t think it`s normal that during one simple setup, memory to go up that high!
When i open task manager during setup, i can see that there is no process that uses the memory that high. The game setup process is using at most 100Mb of memory.
After the setup finishes, the only way i can bring the memory back to its normal usage is to restart the machine.

Anyone else had this problem before ?! And how did you fixed it, cuz it`s braking my nervs really...please help.