You shouldn't have a prefs-1.js file. The normal preferences file name is prefs.js without the -1. You may have a security program or anti-malware application installed on that PC which prevented Firefox from writing to the prefs.js file and the prefs-1.js file was created when Firefox created a new prefs.js file for Firefox to write data into.

You may want to check with Sysinternals to find out why it is writing to that file. http://forum.sysinternals.com/

hi thanks. the interesting thing I discovered is that prefs-1.js is not on the hard drive. so I posted a question in the sysinternals forum that you referenced. we'll see where this leads. right now, I am just more confused by the procmon capture data.

Firefox first creates a numbered temp file with the first available number when a new file needs to be created. Once Firefox has finished with creating the file and writing all data to disk and no error has occurred then the original file in this case prefs.js is removed and the temp file is renamed to replace the prefs.js file. This protects against the case where Firefox isn't able to finish this action what would leave you with a corrupted prefs.js file that could possibly make Firefox crash.

cor-el: thanks, that explains the capture of disk ops to prefs-1.js.