What is the "known hardware incompatibility" that disables PCIe Active State Power Management? How do I fix it?

I'm on Windows 7. I just ran a Power Efficiency Diagnostics Report through powercfg -energy and I got this error:

Platform Power Management Capabilities:PCI Express Active-State Power Management (ASPM) Disabled
PCI Express Active-State Power Management (ASPM) has been disabled due to a known incompatibility with the hardware in this computer.

I did some research in the Microsoft forums and it seems like a lot of people have this issue, but MS hasn't given anyone any satisfactory answers:

If there's anyone at Microsoft who actually knows what the "known incompatibility" is, they aren't saying. After searching Microsoft's website and the web for an answer and finding none, I've come to the conclusion that this is another one of those incomprehensible Windows messages that Microsoft tries to ignore ("...consult your original equipment manufacturer for assistance...") and nobody else can figure out.
_{from: http://answers.microsoft.com/en-us/windows/forum/windows_7-hardware/pcie-aspm-is-disabled-due-to-a-known/6ca12628-42ca-4804-af75-948199a7538a
more: http://answers.microsoft.com/en-us/windows/forum/windows_7-performance/platform-power-management-capabilitiespci-express/8611ba23-8091-46ac-b1f3-97cba5b43455}

Have any SuperUsers encountered this "hardware incompatibility" and figured out a way around it?

Solution 1:

Try unplugging all accessories from your computer (keyboard, mouse, external hard drives, etc...). The error message means that a device that is attached your computer is causing ASPM to be disabled.

My PC stopped going to standby for some reason, and I tracked it down to this error message. I was able to fix the issue by unplugging one of my USB devices (a Playstation controller to PC USB adapter).

Some useful resources for investigating this issue:

• MCE Standby Tool (archived link) - Provides a lot of useful information. For example: the "Windows Idle" tab told me that the "time since last user input" was pegged to 0 (either because ASPM was disabled or the USB device kept sending rogue input.) This counts up when the rogue USB device is disconnected. Hasn't been updated in a while, but the beta version seems to be mostly functional in Windows 10.
• Basic Diagnostics for Hibernate and Sleep. Good list of things to check and explanation of background details like sleep states. Led me to try powercfg -energy