Unable to remove Webroot from legacy computer.

Hello,
 
We were given an older Gateway laptop and it came with Webroot installed. We want to use another vendors malware / virus protection but find that the installed version of Webroot gives us grief.
 
When I tried to uninstall it, a message came up that only the network administrator can remove it. No such thing on my home network.
 
I tried using C:Program FilesWebrootWRSA.exe" –uninstall  and got the same message.
 
I downloaded the removal tool and was messaged that the program was unistalled but it is still there. Ran it as adminstator but the results were the same.
 
In desperation, I removed all the referances to webroot in the registary and it still came back.
 
I am out of options. 
 
I don't know what the serial number is so can't use the cloud tool to remove the sofware either.
 
Any ideas?
 
Henk