Virus remnants on my PC

My child downloaded a video conversion tool from the internet and with it came other files that were too installed in the computer. I noticed them when I did a PC clean up with an antivirus and deleted all of them (as I thought at the time). However, I now notice some unidentified processes running in the task manager. Whenever I look for them in the programs lists in Windows 8.1, they are not available. Where can I find them? How do I delete them?
