unable to open run from start menu

Look at these two reigistry keys, if they both exist. Look for a Value Name
called NoRun. If NoRun exists, the Value Data should be set to 0. If NoRun
does not exist it's the same as being set to 0.

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
CurrentVersion\Policies\Explorer
and
HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Policies\Explorer

Value Name: NoRun
Data Type: REG_DWORD
Value Data: 0 or 1
0 (or not in the registry) = The policy is disabled or not configured. The
Run command appears.
1 = The policy is enabled. The Run command is removed.


Description
Removes the Run command from the Start menu and removes the New Task (Run)
command from Task Manager. Also, users with extended keyboards can no longer
display the Run dialog box by pressing the Application key (the key with the
Windows logo) + R.

This entry stores the setting of the Remove Run menu from Start Menu Group
Policy. Group Policy adds this entry to the registry with a value of 1 when
you enable the policy. If you disable the policy or set it to Not
configured, Group Policy deletes this entry from the registry, and the
system behaves as though the value is 0.

This entry affects the specified interfaces only. It does not prevents users
from using other methods to run programs.

Change method
To change the value of this entry, use Group Policy. This entry corresponds
to the Remove Run menu from Start Menu Group Policy (User
Configuration\AdministrativeTemplates\Start Menu & Taskbar).

NoRun
http://www.microsoft.com/technet/prodtechnol/windows2000serv/reskit/regentry/58876.mspx