Can't download

Recently, I was browsing on the internet and a pop up ad appeared informing me I need to up date Firefox. I had the official logo, so I thought it was legit. I clicked download. From that point on, I lost my original Firefox and was prevented by " something " to re-download it. Avast Tech Support could not remote my computer to figure out what was going on. " Something " was blocking them too. They recommended removing my data with a flash drive and re-installing Windows Microsoft with an installation disc. They could then help me out from there. Is this my only option? Those discs are pricey

via Bleeping Computer Last 20 Posts http://www.bleepingcomputer.com/forums/t/509370/cant-download/