Moved to Malware Discussion > Home User Assistance
First can you boot into Safe Mode?
If so you could initiate System Restore to a time before it hit.
or....try the following removal guide: Remove Trojan ZeroAccess virus (Removal Guide)
Also take a read of my guide which has hints and tools linked all on one page: Anti-Spyware/Malware/Hijacker Tools
Please tell us exactly what you're trying to download - but a simple solution is to download it on another PC, put it on a usb stick and then use it.