My friend has that problem. Once he restarted his computer and it an extra, unclosable process of hl2 was still there, no joke.
Skial
Meowrisa
Blaze Zorah
That's the problem. I can't find it in my processes or anything but I can't uninstall and reinstall steam because even right after I boot up my computer it says hl2.exe is running the files even though it doesn't exist in my processes