Just additional info, for those who have 4GB ram or more on Windows Vista [32-bit], but it displays as 3GB instead, you guys can download Ultimate Windows Tweaker, here
- Ultimate Windows Tweaker v2, a Tweak UI for Windows 7 & Vista | The Windows Club
- Make sure you run it as administrator
- Go to System Performance
- Tick "Enable Support for 4GB of RAM on 32-bit Windows OS"
- Click on Apply