Can you please post a screenshot of the installer alert? That way we see exactly what it says.
Following is a list of registry keys that should be valid until v5.x. See if there are some left overs that need to be deleted.
a. HKEY_CURRENT_USER\Software\ComodoGroup\CFP and HKEY_CURRENT_USER\Software\ComodoGroup\Comodo Internet Security
b. HKEY_LOCAL_MACHINE\SOFTWARE\ComodoGroup\CDI\1 *
*(If you have other Comodo products installed, delete only the values
for CFP)
c. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services cmdAgent
d. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\cmdGuard
e. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\cmdHlp
f. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Inspect
fi. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\cmderd
g. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\cmdAgent
h. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services \cmdGuard
i. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\cmdHlp
j. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\Inspect
ji. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\cmderd
k. KEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Services\cmdAgent
l. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Services\cmdGuard
m. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Services\cmdHlp
n. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Services\Inspect
ni. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Services\cmderd
o. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\cmdAgent
p. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\cmdGuard
q. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\cmdHlp
r. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Inspect
ri. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\cmderd
s. HKEY_LOCAL_MACHINE\SYSTEM\Software\Comodo\Firewall Pro
t. HKEY_USERS\S-1-5-21-1202660629-746137067-2145843811-1003\Software\ComodoGroup\CFP
u. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\Root\LEGACY_CMDAGENT *
v. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\Root\LEGACY_CMDGUARD *
w. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\Root\LEGACY_CMDHLP *
x. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\Root\LEGACY_INSPECT *
xi. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\Root\LEGACY_CMDERD *
y. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Enum\Root\LEGACY_CMDAGENT *
z. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Enum\Root\LEGACY_CMDGUARD *
aa. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Enum\Root\LEGACY_CMDHLP *
bb. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Enum\Root\LEGACY_INSPECT *
bbi. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Enum\Root\LEGACY_CMDERD *
cc. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Enum\Root\LEGACY_CMDAGENT *
dd. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Enum\Root\LEGACY_CMDGUARD *
ee. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Enum\Root\LEGACY_CMDHLP *
ff. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Enum\Root\LEGACY_INSPECT *
ffi. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Enum\Root\LEGACY_CMDERD *
gg. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_CMDAGENT *
hh. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_CMDGUARD *
ii. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_CMDHLP *
jj. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_INSPECT *
jji. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root\LEGACY_CMDERD
kk. HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\CFP_Setup_3.0.14.276_XP_Vista_x32
ll. HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\CFP_Setup_3.0.14.276_XP_Vista_x64
mm. HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\CFPLog
nn. HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\CPFFileSubmission
oo. HKEY_LOCAL_MACHINE\SYSTEM\Software\Comodo\Firewall Pro
To remove the socalled Legacy Keys, which are otherwise hard to remove, open Device Manager from the command prompt using the following two commands:
set devmgr_show_nonpresent_devices=1
start devmgmt.msc
Set Device Manager to show hidden devices under menu option View. Then see if there are Comodo Internet Security related drivers left in non Plug and Play drivers. If so select the driver → click right → uninstall. Do this for all present CIS drivers. Do a reboot when it has been requested.