Turn on firewall Windows XP SP2
I turned off my firewall in the Security Center of Windows XP SP2, believing the firewall in my router (for wireless internet connection) would be sufficient. I want to turn it back on, as I now have regular Trojan horse attacks and the PC sometimes suddenly becomes very, very slow (it executes everything, it just takes minutes). When I go to the Security Center and choose firewall below, the screen appears where I can turn it on, but the option button next to it is inactive. For some reason it's impossible to turn it on.
What can be the cause of this?
Thanks in advance,