Why Can't I Uninstal My Anti-Virus Software?

I have a Dell inspiron that recently broke down while I had Webroot Spy Sweeper With Anti-Virus. I backed up my computer and fixed it, but it deleted all my files and information. I still have Webroot but now it wont open. I checked on my security status and everything is on, but it will not open, so I cant do any security sweeps. I still have a instalation of Webroot left but it wont let me install Webroot because apparently my current Webroot is running. So I tried uninstalling my Webroot, but it won’t let me because it says its running. Can anyone tell me how I can either find a way to uninstal my current Webroot so I can install a new one, or how I can get my current Webroot to work??? I cant risk not having any protection.