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I'm doing some driver development on my Windows machine and I've been wondering why pressing the PrtSc (print screen) button to take a screen capture seems to hang my machine. There are some forums that suggest this happens when the DEBUG boot option is set in Windows and that this is a panic/bug-check in the Windows kernel.

Is this a Windows bug? Or is this actually useful in some way, like in Linux where PrtSc/SysRq is actually a kernel interrupt key?

UPDATE #1: I'm using Windows 7 x64 Professional Build 7601.

Ted Middleton
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  • What version of Windows are you running? There *might* be an option to make the kernel debugger use the SysRq key, but I can't remember. But you'd know if you had one installed. It's more like that [this](http://support.microsoft.com/kb/954436) is your problem. – Cody Gray - on strike Apr 21 '14 at 23:33
  • Windows 7 Pro. I saw that link - but it's for Vista SP1. Surely Microsoft has fixed this since, no? That's what made me think of the SysRq key and that maybe this is actually 'useful' behavior and perhaps I just don't know how to recover the machine. – Ted Middleton Apr 22 '14 at 01:15

2 Answers2

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https://msdn.microsoft.com/en-us/library/windows/hardware/ff541727(v=vs.85).aspx

You can disable the SYSRQ key by editing the registry. In the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\i8042prt\Parameters registry key, create a value named BreakOnSysRq and set it equal to DWORD 0x0. Then, restart the computer. After you have restarted the computer, you can press the SYSRQ key on the target computer's keyboard and it will not break into the kernel debugger.

BriarPatch
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Obviously, you're likely using a usb keyboard, so make sure to add the BreakOnSysRq = 0 value data pair to kbdhid\Parameters (and for good measure hidusb and kbdclass, not i8042prt. This will prevent the PrntScr key from being interpreted as SysRq.

Lewis Kelsey
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