Exactly as Keith says, it could be a Malware infection.
Or there's the possibility that it's a component of Norton Internet Security 2005 which isn't used anymore. It was made defunct by an update, but the task it was connected to may still be running.
If you are running Norton Internet Security 2005, have a read here:
Same as what Keith and Dennis said, but i'm pretty sure its a backdoor trojan that is imitating NTDETECT.COM. I had a similar issue with a process WINLOGO.EXE ( No typo) imitating winlogon.exe