What version of windows are you using? Are sure your dimms are seated correctly? Does your mother board support 8 gigs? Is your OS recognizing all 8 gigs or does also only recognize 4?
I have windows 7, And yea my windows recognize my ram, and my motherboard supports it
Well you shouldn't have to do anything to get AE to use 8 gigs. AE should automatically detect as much as RAM as you have installed. Sorry I don't know enough to tell you anything else. It's early..the pros should be coming round soon. Hopefully they can help you out.
Is it that it doesn't recognize it or that it doesn't use it?
AE is only detecting 4gigs of installed RAM:
When i go to my settings at multiprocessing its says
installed ram: 4096
usable ram: 4096
But i have 8 gigs of ram in my pc.
Open up Photoshop. Make sure no other applications open. Go to the Performance preferences in Photoshop and tell me what it shows for Available RAM in the Memory Usage section. Also - what operating system are you using? If your operating system has a 4GB limit (usually a Windows based operating system), it could be using this as the max even though you physically have 8GB installed.