Windows firewall is broken and can't run anti-virus

When I try to open the firewall settings I get the error message:
"Due to an unidentified problem, Windows cannot display Windows
Firewall settings"

I have merged the "sharedaccess.reg" many times. Each time it
works on the first restart, but the next time I restart I get the same
error "...cannot display Windows Firewall settings".

Also I can't get any anti-virus software to work correctly. I have
tried Norton, Zone Alarm and McAfee.

Here is the history of the problem:

I have Windows XP Media Center with SP2. I have been using Norton
Internet Security 2005 (NIS) since July 2005 with no problems, using
their firewall and running daily virus scans, etc.

On 4/18/06 NIS/NAV virus scan showed a threat, which isn't unusual, I
have had them before with no problems, NIS just took care of them. But
this time was different: From within the Norton Virus scan screen, I
viewed the info about the threat and then the Norton screen suddenly
disappeared. And ever since then I can not bring up any Norton

I have UNinstalled and re-installed NIS several times using the CD.
When I install, everything seems fine, but when I place my mouse over
the NIS icon in the system tray, it disappears. I try running NIS from
the start menu and from shortcuts, but nothing happens. I had the Task
Manager open when I tried to run NIS and the Task Manager shows
NMain.exe briefly but then it disappears again. So I UNinstalled NIS

I tried Symantec's online virus scan, but it wouldn't run. I tried
Symantec's online "fixit" tool, but it wouldn't run either.
They both said they needed ActiveX, but I was allowing ActiveX,
installing them and everything.

I tried McAfee's online virus scan and it worked! It used ActiveX
and it worked fine. But it didn't find any viruses. I tried ZA's
online virus scan too, it worked but again, no viruses found.

Then I tried to install Zone Alarm Security Suite 6 (ZA) from a
downloaded trial. The first time I installed it finished ok. But it
would do the same thing as NIS: It would show the "trial"
beginning screen then when I click to continue it would disappear and
nothing else would happen. I noticed that zlclient.exe would be in the
Task Manager but nothing would show on screen. So there would be no
User Interface showing at all.

ZA wouldn't UNinstall either. It would say that it couldn't login
to the TrueVector service. I had a hard time uninstalling it. I had
to delete everything manually and even had to reboot with the Windows
CD to get to a command prompt to delete vsmon.exe because I couldn't
delete it, even with HijackThis.

I tried the free ZA basic firewall and it wouldn't even finish
installing. It would copy the files and then just stop. I found the
files in the temp folder so I ran setup.exe. Then it would seem to
install. But it wouldn't actually run, it would do the same thing as
the first ZA.

I tried to install McAfee's trial anti-virus. It would show the file
copy but then wouldn't finish installing. So there was no way to
even try to run it.

Now I have no anti-virus software and no firewall, except for the
Windows firewall, but that is broken: I keep getting "...cannot
display Windows Firewall settings" that I mentioned above. And it
works the first time I restart, but after that I keep getting the
message again.
I have tried:
"sharedaccess.reg" (many times),
regsvr32 c:\windows\system32\atl.dll, regsvr32
reinstalling SP2 (twice),
Spybot S&D several times.

Do I have a virus that defeated Norton, ZA and McAfee? Has anyone else
had this? Does anyone have any suggestions that I haven't already

Thank you in advance for any help.