As a Windows PC owner you know this but let's get it out as step 1.
Step 2. With that done, when I want to be sure my PC is pest free, I use Grif's advice at:
Today I was browsing the web and i accidentally clicked an ad. Something downloaded without me noticing and i saw the 'Download finished' icon in Firefox. I pressed the download to see what it was and it opened up my file explorer which showed a file in 'Dvd drive F'. But I only have DVD drive E. My laptop never had a dvd drive F and i know that. I right clicked and pressed eject and it disappeared. Im not quite sure if it's completely gone though. Sadly, i have no images or snapshots of this issue. Any help is appreciated.