Why is all my extra RAM marked as "hardware reserved" in Windows 7?
Turns out that the installed RAM was in an unsupported config -- On this machine, if you install 2GB chips, they have to be installed in triple, as referenced here (pdf).
Its interesting to note that Windows saw the memory, but it was rendered not usable and marked as "hardware reserved".
Ouch, sad to hear about the re-install.
There is a great Mark Russinovich Blog post that explains how windows uses physical memory.
Hardware devices can reserve large blocks of physical address space... To see if a piece of hardware is reserving a large chunk of physical address space, launch "devmgmt.msc", select Resources by Connection in the View Menu, and expand the Memory node. (Mark's blog explains this further.)
Even though your video card has onboard, fast, dedicated video memory, Windows still has to address and interact with that memory using the same physical memory addressing that is uses for RAM, PCI devices and other devices. This can crowd the physical address space. 64 bit OS should cope better with this than a 32 bit OS, but its hands may still be tied some device requirements.
(My Dell has 700 MB hardware reserved on Win7x64. It's not nearly as bad as your issue, but still annoying.)It would be helpful to know if a tool like memtest (which boots and runs without windows) can see all of the installed RAM. Try some of the system info tools on the UBCD to see if they can see (and test) all of your RAM. This would let you know if Windows has even has anything to do with it.
As a final thought, you bought it new from a major vendor, you should be able to get a support from them, and ask them about the issue. They can often get to the bottom of this sort of issue much faster than searching around on the internet, and you've already paid for this service.
Edit: this SO question may be related to your issue, and there is another good explanation of the how memory-mapped IO reservations can reduce the usable RAM. Again, this may not be exactly the problem you are facing, but those blogs tell you how you can determine if it is.
Let us know.
I have this exact problem fixed! With Gigabyte p55a ud3r and Kingston KHX1600C9D3K4/8GX.
When you buy RAM, you get it in pairs, as it turned out each pair/memory stick can only work on memory channel 1 or memory channel 2.
If you put a pair of memory that designed to work only on channel 1, on channel 2 (like I did unknowingly). The BIOS only recognizes them, "BUT" not made available to use. Windows 7 can only see the total RAM installed (in my case 8 GB), but can't make use of the other 4 GBs on memory channel 2, and Windows 7 thinks the 4 GB memory are "HARDWARE RESERVED".
So I advise you to switch them up between the memory slots, like I did, and now I only have 5 MB HARDWARE RESERVED instead of 4 GB like before when I put the RAM sticks on the wrongs slots/channel.