Why won't my computer let me uninstall this unwanted, unasked for program?

My computer has been freezing up for a few seconds, several times a day, for a few months now. It says, “Firefox is not responding.” I’ve done everything I know how to do.
I finally decided to go look at my program list. I’m kind of paranoid because I really f’d up my computer once, when I inadvertently crashed my entire operating system this way…but I got it back.
I saw this one, called “Counter Strike Source.” The publisher is “Valve.”
It installed in April.
When I try to uninstall it it does this. It’s trying to force me to make an account or something and no indication of a further uninstall option.
How do I uninstall the thing?

(I just realized I haven’t tried to uninstall Firefox, then reinstall it yet. I’ll try that too after this discussion.)