Try disconnecting from the internet, unplug/turn off the wireless router if you have wireless/ uninstall comodo and windows defender, then I think if you set msconfig back to normal startup, then use the f8 key to load in safemode, try to rename the hosts file from hosts to hosts.bac or hosts.old. Default location is windows/system32/driver/etc folder.. Then run hostxpert and see if it works or not.. If you still get the error cannot create hosts file.. There is another option.. Boot in safemode, put your windows installation CD in the CD/DVDROM drive, if it opens up a setup screen just close this, leave the windows installation disc in the CD/DVDROM drive, then open start|run and type sfc /scannow (then click ok) the sfc scannow option will compare the system files on the C drive to the files on the CD/DVDROM and replace any that don't match. If your installation disc is not sp3, you may have to uninstall service pack 3 in order to use the sfc /scannow command..

Once this is done, you should restart, then re-install ONE firewall application and ONE anti-virus/malware application that does not have a built in firewall.