The ThinkPad is going through its Power On Self Test. The first set of numbers refer to the amount of memory it has.
173 and 163 means that it has lost its BIOS Setup which probably means that needs a new CMOS battery.
301 is a keyboard error,usually a stuck key.
The request for pasword is coming form the Operating System (Windows) but I am afraid that I will not post how to hack that on an Open Forum (and I hope that no one else will either) because that would be a a recipe for more even stolen laptops. A computer shop can help you there. (With ID and proof of ownership.)
I wouldn't spend too much time and money on the ThinkPad though. 600s are ancient history now.
T, February 2010
