New
#1
That is normal.
Windows 7 is anticipating what applications you may need.
All that RAM will be available if the system calls for it.
Why do you want to lower it?
The reason is the other RAM is cached and You never have the full 4GB. The PC uses it just to run. That is why a sys wont even post without RAM.
Unless your BIOS/Motherboard supports Memory Remapping, you are not going to get the full 4GBs. Otherwise the hardware will continue to take up a portion of the 4GB address space.