Cannot execute any file on computer

It seems someone was able to get administrator rights to
one of the computers in our lab. She has modified the
security setting such that no executable runs. It says
"...due to restrictions on this computer. Contact your administrator."
I am the administrator. I am still able to log in as
admistrator but I cannot run anything: cmd, gpedit.msc,
services.msc,regedit,... on ANY drive.
I do not know how to correct this problem. The computer's
c drive is accessible through the network, so I can
manipulate the files on disk, but I did not know what to
do. I tried remote registry editing but then the computer
was not show available.

Can someone suggest me a way to cure this problem.
Thank you.
Jyoti.