Windows XP SP2 PC. Although user is a computer administrator, it cannot execute ANY program. I have run adaware, spybot and spyware terminator and found no spyware. Logged in as administrator in safe mode. Checked that I could run programs then reverted to 10 days ago with System Restore. Reboot and user worked OK. After reboot - back to same error. Cannot run .exe - message says no permission. Can see .exe through windows explorer. Have run hijackthis - no problems. Can see nothing wrong in services and startup, but there is obviously something running at shutdown or startup.