Windows Vista: Enable 3GB Mode

On 32-bit versions of Windows, the /3GB parameter enables 4 GT RAM Tuning, a feature that enlarges the user-mode virtual address space to 3 GB and restricts the kernel-mode components to the remaining 1 GB.

To run Windows Vista in 3GB mode:
1. Run cmd.exe as administrator
2. Type in the following commands:

bcdedit /set IncreaseUserVa 3072

3. Reboot your pc

To take advantage of the 3GB available to user-mode programs:
1. Backup the program which you want to run
2. Run Visual Studio 2005 Command Prompt as administrator

It is located under: Start -> All Programs -> Microsoft Visual Studio 2005 -> Visual Studio Tools

3. Type in the following commands:

editbin.exe /LARGEADDRESSAWARE your_program.exe

Note:
To disable 3GB mode:
1. Run cmd.exe as Administrator
2. Type in the following commands:

bcdedit /deletevalue IncreaseUserVa

Ref:
/3GB - Microsoft Developer Network
CAD Forum - Enabling the -3GB mode in Windows Vista.
Murray on .NET Building a Monster VS 2005 (or 2008) Deployment Project
C1083 error on linking a VERY large project Visual C++ General Visual C++ MSDN Forums