Accessing 3 GB of memory space in 32 bit OS - LARGEADDRESSAWARE apps

Step 1:
Update boot.ini - change operating system section like following so you have option to boot with both of the option as required:

[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional 3GB" /fastdetect /noexecute=optin /3GB
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /noexecute=optin

Step 2:
use editbin.exe to make app aware of large address space:
edibin.exe /LARGEADDRESSAWARE <app.exe>

editbin is usually in: :\programe files\microsoft visual studio 8\VC\
To change it back: edibin.exe /LARGEADDRESSAWARE:NO <app.exe>

References:
Memory Support and Windows Operating Systems
Additional information and help with the boot.ini
A discussion about the Bootcfg command and its uses
Driver may not be loaded with the /3GB switch
http://support.microsoft.com/?kbid=316739
http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q328269