I suspect that something slipped past Windows Defender and has infected that system - if Defender is all it has. (Microsoft provides it with Windows nowadays - and it's good enough for a first week or two or month or two - I can't say how long and I'm sure it varies. But eventually you need something better.
If you're on a budget (and cannot afford $100 a year major names in anti-virus software), try this:
Your PC needs an anti-virus suite.
In this case, I would advise you to get
which provides (when I last heard) a free anti-virus (no-cost free, that is) for internet security.
Download it, install it, update the anti-virus part fully, then do a Deep Scan or Full Scan on your C: Hard Drive, and eliminate what it finds... this may take an hour or two, but should clean up your PC, and also leave it in a safer condition and less prone to be attacked successfully in future (esp. if you practice good internet practices, don't visit off-color websites, and also take care what emails you open, etc.)
I hope that this helps you get the flash-drive-building working properly, after that is done!