Hi folks, I searched around and didn't see this type of problem addressed, so here it is:
I recently refurbed a Dell Dimension 5150 and I'm using it to dual boot Vista Ultimate 32bit & Xo Pro SP3 32bit.
Here's a quick spec run down:
Socket 775 Prescott P4 3.2 / Dell 0HJ054 Mobo (w/ latest BIOS - A07) / 4 Gb DDR2 (1 Gb in each slot) / 512 Mb GeForce 8400 GS (PCI because I don't have a PCI-e laying around) / WinTV Tuner (PCI) / 2 320 Gb SATA hdd / 2 IDE DVD Writers.
Ok, here's the deal. The BIOS reports that all 4 Gb of ram is present. Windows Vista reports the same. CPU-Z also sees all 4 Gb. Xp-Pro is only reporting 2.74. I removed one module leaving 3 Gb, and XP still reports that 2.74 is present. So, I removed two modules and XP says that 2 Gb is installed. Pop in the third module, and I'm back to 2.74. Pop in the fourth module, and I'm still at 2.74! I understand that a 32 bit OS will map system ram for hardware, but why am I losing an entire Gig of ram? I should be seeing at least 3.5 Gb with all four modules in.
This question has been asked over and over on this forum. Simple answer. 32 bit OS's including your're XP Pro SP3 installation have a limit of 4GB memory address space TOTAL. With 4GB address space available and limited by the 32 bit system, hardware like the video card reserve a part of that 4GB total stealing if you will from the 4GB random access memory installed. It's normal. Vista has a fix to 'show' 4 GB memory installed on a 32 bit Vista installation, but the 4GB Total address space still applies. M$ did this with Vista because this very question has been asked 750 billion times. Install a 64 bit OS to utalize 4GB or more system RAM.
Various devices in a typical computer require memory-mapped access. This is known as memory-mapped I/O (MMIO). For the MMIO space to be available to 32-bit operating systems, the MMIO space must reside within the first 4 GB of address space.
For example, if you have a video card that has 256 MB of onboard memory, that memory must be mapped within the first 4 GB of address space. If 4 GB of system memory is already installed, part of that address space must be reserved by the graphics memory mapping. Graphics memory mapping overwrites a part of the system memory. These conditions reduce the total amount of system memory that is available to the operating system.
The reduction in available system memory depends on the devices that are installed in the computer. However, to avoid potential driver compatibility issues, the 32-bit versions of Windows Vista limit the total available memory to 3.12 GB. See the "More information" section for information about potential driver compatibility issues.
If a computer has many installed devices, the available memory may be reduced to 3 GB or less. However, the maximum memory available in 32-bit versions of Windows Vista is typically 3.12 GB.
I find this onging fix you have supplied, and used so often by so many, to the members of this Forum to render the 4GB XP RAM limitation helpless, if not their entire computer, no longer needed to be mentioned. Ninety-nine percent of XP users are already happily using the M$ feature and all because of you. Paleeseeeeeeeee inform the Forum members of your're fix to the 4GB limit and tell us your're PAE story again. We are all dying to here it.
You stand corrected. Spelling and your're abilities regarding "it"? Bigger question is, why you continue trolling this Forum when no one takes you seriously. It's spelled M$ regarding any concern of yours and this thread.
Now, please tell the PAE story (I won't be listening).