Access is denied. , error from ipconfig, ping, netsh, etc.

Acer laptop, XP Pro, SP2, same symptom SP3, can connect to internet, in
fact I think this started when I went to some "test your security"
sites, which is why I care. I DO HAVE FULL ADMINISTRATIVE ACCESS.
Every time I try to run any network command I know from the command
shell I get "Access is denied.", be it ipconfig, netsh, ping, etc.
I use Comodo firewall and have tried disabling it, to no effect.
I use a WRT54G router and it sees my computer and its network ip
address. Other computers on the network do not have this problem, only
this one. I have tried a repair installation of XP, also with no
change. I also tried uninstalling all network components I could, all
but TCP/IP and then reinstalling them. Nix.
Any help would be appreciated.
Gil

It appears I had underestimated the scope of my problem. I cannor run
anything from the command shell, not attrib, sfc, or winver, to name a
few. I did try other commands, but I forget what. All get me the
cryptic "Access is denied." reply, kinda like the raven.
Any Ideas?

Note: There is a hidden 'Administrator' account (the account name is:
Administrator) in Windows.
Note: The default password for this hidden account is normally blank (none).

For XP Pro users:
At the Welcome Screen, do/press the Ctrl-Alt-Del keys twice to display the
Windows logon box.
Type in "Administrator" (without the quotes), by default the password is
blank, no password need be entered.

Using this account do you still have the same problems?

Thanks JS, Yes, I have tried it logged in as Administrator, same result.
This is the only newsgroup I have posted on, but I have spent many
hours exploring the results of Google searches. I am at the point now of
backing up everything personal and re-installing XP. I will check back
here before I reformat in the hope someone has that simple, elegant
solution.

Try restoring permissions to all objects in the %SYSTEMROOT%\system32
folder. To access the folder's Security Tab to do the steps below
Simple File Sharing has to be disabled. With Windows XP Pro you have to
disable Simple File Sharing in the Folder Options, with XP Home you have
to boot to Safe-Mode.

After you disable Simple File Sharing do the following:

- Right-click on the Windows\System32 folder and select Properties.

- Click on the Security Tab and then again on the Advanced button
(Special Permissions)

- Put a check on "Replace Permission Entries On All Child Objects With
Entries Shown Here That Apply To Child Objects." Click on Apply and
accept to continue at the next dialoge box. The permissions will be
propagated to all the items in the System32 folder, this may take a few
minutes to complete.

[wisling]

For anyone else having this problem...

Try looking at
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\DisallowRun]
or the equivalent on your system.

If you rename the exe file, does it allow you to run the program? If so then try searching the registry for the filename.