When you download a file, you usually have to wait a while for Firefox to finish scanning the file. If you want to turn this off:
1). Open Firefox and in the address bar type about:config
2). Click the button “I’ll be careful, I promise” to proceed:
3). Once this is done, you should see a big list of different settings Firefox is internally using. Scroll down until you find the setting browser.download.manager.scanWhenDone…
4). Set this value to False and restart Firefox.
Now whenever you download any files through Firefox, when it completes it won’t scan your file saving you precious time!
Credit: Thanks to Nirmal’s post “How to Disable Automatic File Scanning after File Download in Firefox 3” for this one. This was very useful for me so I figured I’d share it with you guys!