PC Hangs - Cannot shutdown/or do anything after install of firewall/Antivirus

I installed CPF and CAntiVirus and was waiting to acquire a license to activate; since then the PC hangs and I am not able to start it.

I tried this on another PC - (both affected PC’s run Windows XP Home Edition) and the same. Had to un-install and re-install after acquiring License from Comodo.com

The laptop which seems to be Hung is a business PC-


Try going into safe mode to uninstall it.