Process Monitor : Error Message when I launch process monitor

Clearing the Registry entry worked for me as well.

First you need to close all instances of Process Montior.

Then open regedit.

Find the key located under

HKEY_CURRENT_USER/Software/SysInternals/ProcessMonitor/       for 64 bit version

or

HKEY_CURRENT_USER/Software/SysInternals/ProcessMonitor32/   for 32 bit version

The Key is named Logfile.

Right click on the key to modify.

Set the Value data to an empty string and click OK.

Open Process Monitor.