from one month ago, right after I closed firefox , the firefox would try to modify protected registry key. this happened very often. why? whether my pc have been invaded.? can I allow these modification?
From these alerts, Firefox is trying to add an entry to the Events Log in Widnows. Have you had a look at your logs?
To see the Event viewer, click START - SETTINGS - CONTROL PANEL - ADMINSTRATIVE TASKS - EVENT VIEWER