Photoshop CS4 on Vista not seeing 4 gigs of RAM

Question

I am running Photoshop as part of the CS4 Suite on a bootcamped intel mac pro towers using Vista Business with 4 gigs of Memory. We are running in 32 bit mode because of the Apple screw up with Carbon 64 so that both sides of the house windows and mac match.
Photoshop is currently only seeing 1639 MB of the RAM instead of the performance on the Mac of about 3000 MB
So does anyone know what is going on here and how I can get Photoshop and or Vista to recognize most if not all of the RAM installed on these machines.
Specs are below...
Adobe Photoshop Version: 11.0 (11.0x20080919 [20080919.r.488 2008/09/19:02:00:00 cutoff; r branch])
Operating System: Windows Vista 32-bit
Version: 6.0 Service Pack 1
System architecture: Intel CPU Family:6, Model:7, Stepping:6 with MMX, SSE Integer, SSE FP, SSE2
Physical processor count: 4
Processor speed: 2793 MHz
Video Card: NVIDIA GeForce 8800 GT
Video Mode: 1680 x 1050 x 4294967296 colors
Video Card Driver: nvd3dum.dll,nvwgf2um.dll
Driver Version: 7.15.11.8048
Built-in memory: 2037 MB
Free memory: 1178 MB
Memory available to Photoshop: 1640 MB
Memory used by Photoshop: 55 %
Image cache levels: 4
Application folder: C:\Program Files\Adobe\Adobe Photoshop CS4\
Temporary file path: C:\Users\MGD\AppData\Local\Temp\
Photoshop scratch has async I/O enabled
Scratch volume(s):
C:\, 349.4G, 324.0G free
Primary Plug-ins folder: C:\Program Files\Adobe\Adobe Photoshop CS4\Plug-ins\
Additional Plug-ins folder: not set

Answer 1

While Jim's suggestion is the only solution to addressing all your system's memory, I am surprised you only have 2037 MB (built-in) memory. Perhaps you are running processes or have devices attached which are eating into your memory by as much as .5 MBs?
I also have 4GBs installed ram. Right off the top, Windows strips 1 GIG to reserve space for Video Cards and other devices. I lose another .5 MB to the system.
This is a well-known limitation of 32-bit systems and like Jim says, there is little to be done except to upgrade to Vista 64. You can remove devices and stop processes and services, but you'll not ever see . . . at very best . . . 3.5 GBs. (Well, you might by using the /PAE switch, but that is more risk than I'm willing to play with.)
This is what my system looks like:
Operating System: Windows Vista (Ultimate) 32-bit
Version: 6.0 Service Pack 1
System architecture: Intel CPU Family:6, Model:7, Stepping:7 with MMX, SSE Integer, SSE FP, SSE2
Physical processor count: 4
Processor speed: 3666 MHz
Video Card Vendor: NVIDIA Corporation
Video Card Renderer: GeForce GTX 280/PCI/SSE2
OpenGL Drawing: Enabled.
Video Card: NVIDIA GeForce GTX 280
Video Mode: 1920 x 1200 x 4294967296 colors
Video Card Driver: nvd3dum.dll,nvwgf2um.dll
Driver Version: 7.15.11.7740
Built-in memory: 2557 MB
Free memory: 1281 MB
Memory available to Photoshop: 1640 MB
Memory used by Photoshop: 60 %
Image cache levels: 4
Thus far, I've not encountered any problem using a 32-bit version. That is partly because I've not done anything with PS or other applications which might cause problems. But, as I do more with the Master Suite I expect that situation to change. Then, I'll upgrade to Vista 64.
I'm kinda keeping my eyes and ears open about Windows 7. Unless I encounter performance problems, I'd rather wait for the next version. According to rumors, the earliest date would be the end of the year, if not early 2010.