Take a careful look at this picture - something* is very wrong.
Your first natural thought is probably that I simply have my cache set to ~500 MB or so. Wrong.
I don't think I ever adjusted my cache settings. Right now FF claims it's using a mere 50 MB for the cache.
If you're totally clueless to the cause of this issue welcome to the party cause I am too.
A weak shot in the dark would be addons, skins and all that other stuff.
Wrong. Wrong and wrong again.
A quick trip to Explorer clears up the confusion. I have two rather large PS (post script) files (200+ MB a piece). These are the results of some fairly large File->Print->Print to file operations.
So if you discover your Firefox (or whatever else) installation size is OFF THE CHARTS check out the folder in Explorer. Chances are it's just some other files laying around throwing off the numbers.
* Bonus points if you noticed that Windows gets the "last used" date all wrong. The screen shot (like this post) was taken @ 10/26/2007 however WinXP claims FF was last used on 10/22/2007. I've used FF at least 100 times since 10/22 !