Windows May Not Detect All 4 Gigabytes of Memory InstalledAffected Products: Software
Affected Operating Systems: Windows Vista, Windows® XPISSUE: On a computer with 4 gigabytes (GB) of memory installed, the amount of system memory (RAM) reported by Windows XP or Windows Vista 32-bit may be less than you expect. For example, on a computer with 4 GB of memory physically installed (4096 MB), Windows may report 3120 MB. The BIOS correctly identifies 4 GB of RAM. RESOLUTION: This is by design. A 64-bit version of Windows Vista does not have this 4 GB limitation.
To work around the problem, install Windows Vista SP1. Windows Vista SP1 modifies the way Windows reports the amount of installed RAM. It will report total physical memory installed, rather than physical memory made available to the OS by the BIOS. Functionality remains unchanged but once SP1 is installed the user will see 4 GB RAM when 4 GB is installed.
For example, before SP1, the amount of RAM shown may be 3324 MB.
After SP1, the amount of RAM shown is 4.00 GB.