nt keeps shutting down

i keep getting the message “the evaluation period for your windows nt has expired and nt will shut down within an hour. please upgrade to a licensed copy.” nt then proceeds to shut down. the copy i had was a fully licensed copy. i however borrowed afriends licensed copy and used it to upgrade but i got the same results. could there be a virus affecting the system? also, when i check the event viewer after re-booting, i get the message “nt recovered from a bug check.