Experienced a mysterious (to me) change this morning.... initially with fireFox 2. and while trying, in a quickest manner possible, to resolve the change... did a install of FireFox 3 but that did not correct that unwanted change as seen with Firefox 2...
I am running OS Vista in one of my 2 online computers. see *Note
FireFox 2 usually displayed only one Tab seen on the bottom Bar of my Desktop that used to display a drop-down/drop-up Box showing all open Browser Windows when mouse left button click.
*Note: There was no change found with my laptop which runs on OS XP on FireFox 2.
This previous ability to display all multiple open Browser Windows by simply clicking mouse left button on the FireFox Tab (still found at the Bottom Bar... but no longer works as before with mouse left button click) mysteriously vanished. Instead... a (new to me) list of Tabs now appear at the Top of Window (much as a additional Tool Bar does) .
To clarify: The Mouse Left Click no longer functions as opening a New Window as it did previously. Instead now I have to click the Mouse Scroll (acting as a Mouse Center) button as the only method that will open a New Window.
How this change (disabling the left mouse click function which used to activate a display of all open windows) happened by simply shutting down the computer then re-starting up the next morning is to me unknown.
Nothing new had been been knowingly installed other than seeing 2 fireFox 2 add on-updates/install/continue messages without any noticeable change while continuing to use hundreds of times prior to shut down... AVG database update is the only other install.
This computer has been clean of any malware since purchase. Have Comodo Firewall and Boiclean. Spybot and Ad-aware +more that find no problems since CCleaner seems to eliminate all.... AVG 8 runs every 24 hours. CCleaner is used more often than every hour if involved with PTR. Thus fairly confident that No Trojans etc exist...
Next: Invoking a previous Windows Restore Point did not return (neither the mouse Function to left button nor did restore-restore the Tab configuration allowing a drop-up/drop-down box display) to the original state.
Hmm... All I did was shut the computer (vista) off overnight and encountered this change this morning and the cause of this change still eludes me has locked me thinkin cap in a confused

state.
Anyone got a explanation of what could have caused this and a workable suggestion how to return to original state?
Question: Does the original cause of problem and solution lie within Vista or within FireFox
Perhaps a simple uninstall/reinstall of Firefox might solve this problem? but that would negate learning of easier alternatives...
Any TIPS?
I'd rather have a easy way out answer here from one who has experienced the same problem and replies knowledgeably than possibly having to waste a few hours

trying to figure this nuisance out on my own.

Thanks in advance.