I don't think you want to go in a full procedure of analysis/removal. So we'll try something simple.
Attempt uninstalling Internet Download manager.
Install Malwarebytes and do a full scan.
After that, try downloading a file with a browser without any third-party programs interfering.
If you still have problems with that, and wish to attempt an advanced analysis, contact me via PM so we won't flood this section!
Best of luck!