Windows 7: RAM available for a process limited?

I was wonder why my Adobe After effect often not responding when I preview large file. After several research, I find out that window only allocate about 1GB RAM for all process (I have 4GB RAM installed in my desktop) even there are still many empty space available. I run 2 different program and task manager show that usage of 80%++ RAM (about 3.5G total physical memory usage) is possible. How can I increase memory space for a program?

Programs have no concept of memory - they use virtual address space, which abstracts memory from the process. The memory manager in the kernel of the OS is responsible for mapping pages of virtual address space from a process either into RAM or the paging file (or both, in a lot of cases). Since you're using Windows 7 x64, each process will "see" that it has 8TB of virtual address space available to it to load and use as "memory", and can use that space how it likes. When you are in this situation, run resmon.exe and look at the memory tab's data to get a better idea of memory usage on the system - task manager is pretty poor at giving accurate and usable memory statistics.

Congrats, you finally figured it out

I once debated this with you at msfn.org. It was about PAE, 32bit applications and physical memory above 4G. You banned me, because I said (you said the opposite) that applications don't need to be "PAE"-aware to be physical located above 4G.