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I tried to install com0com - a null modem emulator - on Windows Vista, but failed because Windows Vista doesn't let me install a driver that is not digitally signed.

I followed these instructions found in the readme file:

  1. Inactivate UAC
  2. Run bcdedit.exe -set TESTSIGNING ON
  3. Reboot the computer.
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up vote 4 down vote accepted

Try running bcdedit.exe -set TESTSIGNING ON in an administrator command prompt (Run as Administrator). Or try: instead.

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Thanks, the problem was that I wasn't logged in as an Administrator when I run the command the first time. – Jonas Jun 30 '10 at 11:26

Is 32 or 64 bits Vista? I remember reading in the OSR mailing list that unsigned drivers can not in any way be installed in vista 64 bit. Hope this helps.

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It's 64 bit. I got it working now, see the answer by BloodPhilia. – Jonas Jun 30 '10 at 11:27

For anyone having the driver signing issue on Windows 8, the bcdedit answer above doesn't seem to work because Windows 8 has some sort of new Secure Boot policy that prevents running that command successfully, even as admin (on my machine, at least).

What worked for me was running shutdown /r /o /t 00 as admin, then selecting Troubleshoot, then Advanced options, then Startup Settings. Click the Restart button to restart and enter the Startup Settings menu, then select option #7 (Disable driver signature enforcement). After restarting, Windows should now allow installation of the com0com drivers (though it shows big warning messages that the drivers are untrusted).

(I found the details on getting into the advanced startup settings here.)

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