My company recently built a new Exchange 2000 Server computer with 2GB of RAM. However, Exchange doesn't seem to be using all the RAM, and the computer sometimes complains that virtual memory is low. How can I fix this problem?
Windows allocates a default virtual address space of 4GB: 2GB for the kernel and 2GB for each user-mode process (e.g., store.exe). This allocation occurs even on computers with small amounts of RAM; that arrangement is OK because the point of having a virtual address space is to provide a range that's larger than the available physical address range. Unfortunately, when the physical address range is no longer larger than the virtual address space, Windows can run out of virtual address space, causing the problem you describe.
To fix this problem, Windows NT Server, Enterprise Edition added a boot-loader switch that tells the kernel and virtual memory manager to tune themselves for large amounts of physical RAM; Windows 2000 Server OSs use the same switch. Add /3GB to the end of the boot.ini line for your default OS, then reboot.