My wife just bought a laptop with 4GB memory installed. When she reached home, she just realized that from the Windows system, the configuration stated,
Installed memory (RAM): 4.00 GB (2.00 GB usable)
She suspect the RAM is faulty but actually it wasn’t (she tested the RAM on other laptop and it’s working fine!). After been “googling” around, she have came across Memory Limits for Windows Releases article from Microsoft. It’s not the faulty RAM, motherboard or other hardware. It’s just because the laptop was installed with Windows 7 Starter version!
Physical Memory Limits: Windows 7
Windows 7 Ultimate / 4 GB (x86) / 192 GB (x64)
Windows 7 Enterprise / 4 GB (x86) / 192 GB (x64)
Windows 7 Professional / 4 GB (x86) / 192 GB (x64)
Windows 7 Home Premium / 4 GB (x86) / 16 GB (x64)
Windows 7 Home Basic / 4 GB (x86) / 8 GB (x64)
Windows 7 Starter / 2 GB (x86) / NA (x64)
