Problems installing Comodo Firewall.

Since August 2007 I’m enjoining Comodo Firewall.
Last weekend I’ve noticed that nor my AVG antivirus nor Comodo Firewall was working.

AVG was easily re-installed. Comodo Firewall not.
When I tried to re-install, I always get the notification: “the Comodo Firewall is already installed, do you want to uninstall it?”.
Thinking that after clicking the yes button, my problem would have been solved was wrong.
Searching my computer for the words “firewall” or “comodo” nothing was found.
Can somebody help me with my problem?
One positive point in the matter is that now I’ve installed the Comodo Antivirus software.
But I’ve got no firewall. Does Comodo have a solution?

Go to Start → All Programs → Accessories → System Tools → System Restore. Choose “Restore my computer to an earlier time…” and click OK.
From the calendar, choose a date and time when you know the PC was working properly and then click Next. Follow instructions onscreen to close open programs and then click Next. The PC will reboot and the operating system will wind back the clock to the date and time you choose.

Why did you think Comodo had ceased working?