Why do I have less memory with 32 bit OS [duplicate]

There's a great table here on Wikipedia showing the maximum addressable physical memory for various versions of Windows.

First of all, a 32-bit OS using PAE can use more than 4GB of RAM. Second, yes, it appears true that no version of 32-bit Windows 7 has this feature enabled.

The good news is that there are 32-bit versions of MS Windows which support more than 4GB of RAM. The bad news is that they don't tend to be aimed at consumers, so I hope your company will buy them for you! They are:

• Windows 2000 Advanced Server (8 GB) or Datacenter (32 GB)
• Windows Server 2003 Enterprise Edition (16 GB), R2 Enterprise Edition (64 GB), R2 Datacenter (128 GB), or Datacenter Edition (16 GB)
• Windows Server 2008 Enterprise, Datacenter (64 GB)

A 32-bit OS, using 32-bit pointers, can address 2^32 bytes of data, which is 4GB.

On top of that, in an x86 architecture, the first 1MB is spoken for by legacy hardware memory addressing. On top of THAT, your video card's memory requires address space in the same addressing scheme, so the more video card memory you want to be able to address, the less RAM you can access.