For those even less familiar with Command Prompts than me: to run the imagex command string as given in Comodo’s Step 2 for Win 7, the command must be run from the directory containing the imagex.exe file. In my case, I’ve installed Windows AIK to c:\Program Files\WAIK and, as I’m working in 64-bit, the appropriate sub-folder containing the imagex.exe file is c:\Program Files\WAIK\Tools\amd64 . Therefore, to run the Step 2 imagex command successfully, it would be necessary for me to first enter cd c:\Program Files\WAIK\Tools\amd64 at the command prompt [followed by “Return” of course] to then run the imagex command string, which in my case would be imagex /mountrw c:\winpe-amd64\winpe.wim 1 c:\winpe-amd64\mount (The “1” is indeed a numerical 1 rather than an alphabetical l.)
Edit: While Step 2 is the point at which changing directories in the Command Prompt becomes necessary to run the relevant *.exe file (imagex.exe for Step 2), the same applies, of course, to subsequent steps. Search through your WAIK folders for the one containing the relevant *.exe file and then change directories (cd C:.… etc) before running the associated command string given in the Comodo guide.