I discovered this problem after a fake antiviral software popped up and told me I had problems. I already had NOD32 running so became suspicious. I ran Malaware bytes which found some problems that I then deleted. I ran a manual scan with NOD32 which found the Medfos (although it hadn't previously spotted it) but can't delete it. So, I have run the procedure detailed on this forum and am now uploading logs. I have an XP64 bit system so didn't run Combofix or RootRepeal. So far, there seem to be no symptoms/problems but when I reboot I get the warning from NOD32 about the virus. I've unplugged 3 back up drives that were attached, one of which was my Dropbox folder. Thanks for any help.