Yep, while 32-bit Windows can technically access up to 4GB of memory, some of that address space will be used for things like your graphics card, so you won't be able to access the full 4GB of system memory.
MERGED QUESTION Question from veeresh kumar : "showing less usable memory"
i HAVE WINDOW 7 PROFESSIONAL 32 BIT. CPPU INTEL CORE DUO E8400 2 RAMS OF 2GB EACH 800 MHZ.
THE WINDOW SHOWING MEMORY 4 GB BUT USABLE MEMORY AS 3.21 GB. PL HELP
Yep, while 32-bit Windows can technically access up to 4GB of memory, some of that address space will be used for things like your graphics card, so you won't be able to access the full 4GB of system memory.