I have successfully uninstalled
Thanks to this post by Whited Lightning:
http://forums.comodo.com/help_for_v3/windows_cannot_access_the_specified_path-t23860.0.html;msg175199#msg175199Solution? See other posts at this site... search for "cannot access".
For me, this is what worked. The idea is to get explorer.exe to be a trusted application again.
open the Windows Task Manager by
hitting CTRL+ALT+DEL. If the latter, click "File", then "New task (run)". In the "Create New Task"
window that appears, type exactly this: "file:///C:/Program%20Files/comodo/firewall/cfp.exe".
(Assuming you installed comodo in the default location. If not adjust the path above accordingly.)
Hit "OK", and the firewall window should open.
Now, as stated in other posts, go to "Defense+", "Advanced", "Computer Security Policy".
Find explorer.exe and make it a trusted application. Don't forget to click "Apply".
I then followed this post below by Pandouk:
http://forums.comodo.com/frequently_asked_questions_faq_for_comodo_firewall/manual_uninstall_of_cfp_2x-t5326.0.html;msg39350#msg39350If you have problems uninstalling or reinstalling CFP, download "comodo Uninstall.zip" and extract both "clicapi.dll" and "fwconfig.exe" in the C: directory.
Then at the command line of windows use the following command:
c:\fwconfig.exe -uninstalln
After finished reboot your pc and eliminate
C:\Program Files\Comodo\Firewall
I now have no comodo

This worked for windows xp, not sure about vista, i didn't install it on my vista machine.