Windows – Can I make some of the hard drives invisible to certain programs

I had a similar case. I solved it by disabling the drive controller (as a hardware device) and enabling it when needed. When HDD controller device is disabled, Windows don't touch the drives at all. I used devcon.exe command line tool which can disable or enable hardware driver by its name and path. In my case the commands were:

  devcon.exe disable "@PCIIDE\IDECHANNEL\4&*&1"
  devcon.exe enable "@PCIIDE\IDECHANNEL\4&*&1"

devcon.exe is the console version of Microsoft's device manager. You can get if for free from Microsoft, read more information here: http://msdn.microsoft.com/en-us/library/windows/hardware/ff544707%28v=vs.85%29.aspx

The path to the device in my particular case is @PCIIDE\IDECHANNEL...; you can use devcon.exe to find the path to your device.

Note that I agree with comment of Ramhound: What you trying to do goes against the basic principles of operating systems. So I would recommend to let Windows manage the drives by itself. (The reason why I did these strange things was I had hardware issues and manual disabling of drive controller this way was necessary to let Suspend to RAM feature work correctly on my mainboard.)

I have seen some programs (especially RAM-drive software) that purport to being able to access the “unavailable RAM” on 32-bit systems. That is, even though Windows cannot see or access some of the 4GB that is installed on a 32-bit system, these programs claim that they can.

I guess technically this is possible if the programs manages to insert itself early enough to activate either PAE or 64 bit mode, and then emulate normal operation to the OS before it finishes loading.

On my 32-bit system with 4GB, Windows sees only 3.20GB, but so does the BIOS.

This is because a 32 bit system has 4 GB address space. Part of that (ideally 512 MB or less) should be used for the RAM. The rest is for PCI address space, virtual memory addresses etc.

It is not a matter of using PAE or the /3G switch, because it’s not a Windows limitation, it is a motherboard limitation. If the chipset and memory controller can’t access beyond that, then I don’t see how Windows or any software can either, even if they access the hardware directly.

True. If your memory controller or the motherboard is limited to 4 GB then that is that. Game over.

I know that using PAE requires using either a server or 64-bit edition of Windows

No. This is wrong.

PEA works on a 32 bit OS. It uses 36 bit addressing. Think of it as 16 (2⁴) windows of 4 GB (2³²) each. Or think of it as a book with 16 pages. You can not see more than one page at the same time, but you can turn the pages.

(though I don’t see how even these versions of Windows can access what the BIOS cannot). However these programs say nothing about that and imply (or outright say) that they work for normal users with consumer versions of Windows.

PAE is an option on these windows operating systems, assuming that the hardware supports it.

• Windows 7 (32 bit only)
• Windows Server 2008 (32-bit only)
• Windows Vista (32-bit only)
• Windows Server 2003 (32-bit only)
• Windows XP (32-bit only)

Source.

As you can see that is on 32 bit OS's only. Both the server and the consumer versions. I seem to recall that it was later removed from windows 7 SP1, though that is not mentioned on the MS site.

I have tried a couple of these programs (specifically RAM-drives), but was not able to have it access the upper memory. Does anybody know if there is any truth to these programs’ claims? Has anybody actually seen it work? And if so, how exactly do they pull it off?

Without knowing which programs we can not answer that.

However they might work on a motherboard which supports PAE, but not on a motherboard which either lacks the copper traces for it, or whose memory controller does not support it. (e.g. old CPU's, old chipsets, atom CPU's older than Pineview or Diamondville).