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I am running Windows 7 (64-bit) and have noticed that in the last couple of days (right around when I bought a new monitor, oddly) it has started to take a short while to resume.

So I typed "Performance Information and Tools" into the Start Menu to get the Windows Experience Index screen and then selected the "Advanced tools" option to get the following:

enter image description here

When I select the first exclamation, I'm presented with the following:

enter image description here

A Google search for "WUDFRd.sys" gives me a couple of forums with people complaining that it causes errors, some (seemingly) dodgy advice on removing it and a number of very suspicious sites that claim that it is a virus.

My questions are:

  • What is a "user-mode driver reflector framework"?
  • Why is it causing Windows to resume slowly?
  • Is there really a problem and, if so, how do I fix it?

(footnote: all drivers are up-to-date, all Windows updates are installed, Microsoft Security Essentials is installed and I've done a full scan)

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What is this UMDF thing?

UMDF enables certain classes of drivers (mostly USB-based or other high-latency protocol buses), such as those for video cameras, MP3 players, cell phones, PDAs, and printers, to be implemented as user-mode drivers.

Source: Windows Internals

UMDF, also known as User-Mode Driver Framework, came with Windows Vista as to provide a separation for drivers to running in User mode and in Kernel mode. The important difference that this provides is that when you attack a device (like a USB stick) that it does not need privileges to the user but can just run in the user context, such that you don't need to accept an UAC prompt or the like when you attach a USB stick to your computer.

So, it could be seen as a layer between the OS and those drivers / devices.

A further overview can be seen at this URL, the most important part here is the UMDF reflector:

The reflector is a Microsoft Windows Driver Model (WDM) kernel-mode driver that permits an application and a driver host process to communicate. The reflector creates a separate device object for each device instance and handles Plug and Play (PnP) and power I/O requests associated with each device instance. All communication between the application and the driver host process happens through the reflector.

Overview of the UMDF - Reflector

Again, this serves as a layer, but this time between the drivers / devices and your applications.

So, why is it slow in my case?

I'll tell you at first that it isn't slow. It's just a layer that doesn't impose much overhead, but then you might wonder why you are still getting that warning. Let's take a closer look draw a free-hand ellipsis...

Right! So, that means Internal Storage is what is causing the problem here. Well, this doesn't tell much on its own though, that's why you should check the event log for more details on what device exactly is causing this problem and troubleshooting what might be wrong with that device.

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Many thanks for the explanation. When I clicked on the "view details in the event log" link, it turned out that it was the Intel N10/ICH7 Family USB Universal Host Controller that was generating warnings. Further digging showed that it was on version 6.x.x.x so I downloaded the updated drivers (9.1.1.1016) and so far nothing new has been reported... –  Richard Jun 27 '12 at 22:09
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