Be wary, I think regular 32-bit versions of vista will only recognize 3GB of memory. Incidentally, it's a piece of cake depending on the computer. My dv1000 was just a little screw and snap in and out.

Yeah, I routinely see ads written that way. It's often matched pairs.

Yup. To go past 4gb requires either Vista 64 or XP 64. Furthermore, some other things intrude into that 4gb space. I've seen numbers from 2.8gb to 3.5gb actually available on various machines.

You also have to be sure the hardware chipset supports the max memory, in addition to the OS variant. Example, Vista 64 on a laptop is limited by shiset hardware. I had these things bookmarked from a recent infrastructure project:

Microsoft's list of the memory limits by OS flavor:
http://msdn.microsoft.com/en-us/libr...78(VS.85).aspx

Intel's lists of max memory by Laptop ChipSet type:
http://compare.intel.com/pcc/showcha...&culture=en-US
These are laptops, other chipset types, desktop, server, etc are here.

And there's a guy who did a quick test on some Lenovo ThinkPads and captured the images from the My Computer > Properties list. It shows what you're referring to, something less that the total in the MS and Intel lists.

My Dell desktop running 32-bit Home Premium reported about 3.3GB free. I've since gone to x64, so that's no longer an issue.

It's not a "technicality," but the maximum amount of memory any 32-bit operating system can address is 4 GB; memory addressing space reduces that to somewhere around 3-3.5GB of usable RAM.

If you have a 64-bit operating system, the amount of memory that can be addressed jumps up to a few terabytes. In my office at work I have a $12000 Dell workstation with 32 GB of RAM installed. It's running Windows XP x64.

The amount that Vista Ultimate can access will depend on whether it's the 32- or 64-bit version as well as the particulars of the motherboard chipset, processor, and memory controller.

Another Crucial rant
 

Added Crucial memory to a Toshiba laptop, so I had one Kingston chip, one Crucial. Wouldn't boot. Bought another from Kingston. Booted.

So...my experience has been: Kingston good; Crucial bad.

(But Crucial's memory analyzer is very good.)

Here's 4GB of nice OCZ laptop RAM for $53 after a $30 rebate, good only for the rest of today:

http://www.buy.com/prod/ocz-4gb-2-x-...204887399.html

You might also have booted with two Crucials. Some boards are very sensitive to memory that's not perfectly matched.