Firefox Portable doesn't backup/restore the Crash Reporter keys. This is the preference under Advanced -> General -> "Submit Crash Reports".
Steps to Reproduce:
- Start Firefox Portable
- Go to Options
- Hit the Advanced tab, then General
- Disable
Submit Crash Reports
- Close Firefox Portable
- Observe that a registry value has been created without cleanup.
HKCU\Software\Mozilla\Firefox\Crash Reporter\SubmitCrashReports
If local Firefox is installed, the crash reporter key will already be created. Delete the values beforehand to test.
I talked to JohnTHaller on IRC about this a while back. I believe this is a known bug, just leaving this here for reference.
This bug is introduced in Firefox 16. Ironically, I made the patch to create this registry key in bug 577221.