Ever since I started using Firefox the same thing happens to me every time I download something. If I miss that little pop up box in the lower right corner, I'm screwed - searching forever...
On the top bar in Firefox Tools->Downloads will take you the default download location.
You can change the preferences to prompt you for a location for each download or change the default location (to something you'll remember
AV related, finished moving ~400 seats to AVG9 last week. Smooth upgrade - only a handful required manual intervention.