Last night, I downloaded a flex test for Unity Engine 4 that was previously virus-free. When I attempted to download the file last night, I got everything running fine, the project worked and everything. There were multiple bundled viruses, but I declined all of them, making sure I pressed 'Custom Install' to make sure everything was unchecked, so I thought I was safe. One thing I didn't immediately notice was that the download, even though I took precise care to make sure I didn't download any bundle, was still riddled with viruses. Windows Defender took out most of them, but it left one quite big one that was causing issues. I then installed MalwareBytes, but it turned out that the virus completely prevented the program from opening. I tried with Avira, and it detected quite a few and removed them. I identified the infected folders in my Program Files (x86) folder as "regtool," "svcmx," and "qdcomsvc." There were previously four or five, but they've since been removed. I cannot delete the folders upon a normal startup, and I have to go into Safe Mode to delete them, but they return upon normal boot up again. There also seems to be a process running, that, when terminated, returns again only a second or two later. The virus has changed my default search engine on Google Chrome to a popup infested version of Yahoo!, and it cannot be changed, no matter the settings on Google Chrome. It also will entirely close out of my Chrome on occasions, seemingly to try and prevent me from getting any way to remove it. I uninstalled Chrome at one point, and had to be installed in Safe Mode because it would not install on a normal boot up. To remove the virus, not only did I attempt using a few different antivirus, but I deleted the folders in my Program Files (x86) as previously mentioned, and I also found versions of the folders lurking in my AppData folder, which also had to be deleted in Safe Mode. No matter what I do, and how much I delete, all the files and folders always return on a boot up.