Are you sure you made one copy? And in the same folder? I would check in the copy settings if there is an absolutely unnecessary reserve somewhere. More than once it happens that along with the installation of the mod, the source quietly slips you some more files into the download. A couple of times I picked up viruses like that, installed some strange browsers, molded by novice designers. In general, any garbage came across. Another bad role was played by caution with saving copies on RAID. When you infect not one disk with a virus, but two, working with different RAID failure scenarios becomes more complicated.