Internet is slow after downloading Windows 7 files. What to do?

Last night, I downloaded Parallels onto my computer and everything was fine. I then downloaded the Windows 7 files from the Microsoft Store and the download speed was excellent -- took about 30 minutes to download ~300 GB of files. After attempting to click on these files to open them, they wouldn't open, and I realized that I should have purchased through the Parallels online store.

Shortly after this, I realized that my Internet speed was very slow, maybe 2-3 KB/sec. I uninstalled Parallels and cleared the Windows files from the Downloads screen, but Internet was still slow.

Installing Windows can wait for another time (and maybe I'll just use Boot Camp instead). For now, all I want is to get my fast Internet speed back. Any suggestions?