"NTLDR missing" is usually caused by corruption of that file by a virus/worm, or someone unknowingly deleting it to clean out the "C" root, thinking it's not important. Can happen too, when that same type of "unknowing" person edits the boot.ini file & corrupts its' accuracy.
Other Boot.ini problems usually just hang the boot with no message.
As to the vlk user. What systems technician, in an Enterprise scenario, taking care of maybe 300-400 units, is going to be walking around with a boot stick? With which he's going to have to re-activate (not reregister) no less.
Edit: That last sentence is completely wrong in fact! As pointed out to me by Truth. I do know better.
He doesn't have time for this. They do very quick replacements to get the worker back up at his (her) own station. The boss is expecting a 10-15 minute turn-around. Technicians learn real fast to change hd's, monitors, nics, power supplies, cpu's, and entire comps in under 15 minutes. Or, he's out of a job. He is definitely not going to be playing around with a boot stick.
When the hash fails, the boot just hangs. Have to do a repair install, which will work most of the time, if it's not a completely new rig.
Edit: This also has to be qualified. In a Corporate Pro situation, there is no hash to become problematic. But very true in small to medium sized businesses.