How do I turn off Avast in order to download a file that is not downloading properly?
What version of avast are you using free/pro/ais ?
Why isn’t it downloading (errors, etc) ?
What (and where) are you trying to download and we can see if we can download it ?
avast doesn’t block, just scans and alerts to infection.
Just don’t do that… You don’t need it 
I’m running Avast Pro 5. I’m trying to download software for my Passport Elite: Mimeo
wdanywhere. I keep getting an NSIS ERROR INSTALLER INTEGRITY CHECK HAS FAILED. CAUSES ARE INCOMPLETE DOWNLOAD AND DAMAGED MEDIA. CONTACT THE INSTALLER & AUTHOR TO OBTAIN A NEW COPY. So far WD has solutions have been to delete cache, disable antivirus, etc. I wanted to disable Avast but do not see a way to do that.
Well… You shouldn’t disable the antivirus when you most need it… downloading and installing software…
Right click the icon > avast! shields control > …
Can’t find Avast Shield control. What I see is “real time shields”
Did you ‘right click’ the Avast icon (Ball)? You should see Avast Shield Control just above 'Silent Gaming Mode! 
crsaj
Contact WD I saw one other post today where somebody was trying to download a WD firmware update and Zone Alarm Security flagged it as a virus. Their software/firmware sucks big time. Every time they do a firmware update their forum is loaded with people with messed up external HD.
Joe
Here is a little more on the problem look at post 3 http://community.wdc.com/t5/My-Passport-for-PC/virus-detected-in-my-passbook-essential-3-0-firmware-update-1/td-p/126068
Apparently it is their firmware on a circuit board on the external drive communicating through USB port causing the problem.
Joe