...this happened late one night so I left it alone till morning when I tried to power it up again. Again, it sounded the alarm and I pulled the plug before it went any further.
I opened the case and just looked around and saw a (second hand, from a friend's PC) bank of 256Mb Ram memory I had installed a few days earlier to be apparently not fully home. I pushed it home and also pushed home just just about every component to eliminate such obvious step from a basic troubleshooting sequence. I powered the PC again and this time no alarm sounded, all air coolers (power source, CPU and video card) and the HDD went to work and sounded as they use to do before break down. But nothing else happened. No boot-up sequence on the screen, nothing.
As this point I took my PC to my neighbourhood friendly PC technician, who tried pulling out every card (but the mother board) and replaced them, with equivalent cards from a working PC, first one by one , then in various combinations and eventually all at once, to no avail. He replaced all test cards in the "control" working PC to make double sure they were still ok after having served as "working controls" on the broken PC. This prompted his veredict as: "we have here a faulty mother board" which it very well is the correct diagnosis"

He finally "slaved" my PC's HDD on his good working PC to make sure it was operating, which it was.
Except for, HORROR OF HORRORS !

As on occasion, a visiting friend will ask to check his/her email o my PC, I had made up two (Windows XP) accounts. One for myself, at Administrator's level with full privileges, with a User I.D. and a password and a second account with limited privileges, without a password, for visitors.

As it happened, as a "slave" storage medium, hooked to a working PC, my HDD will only show and made accesible data stored in the "visitors, non-password windows session". No mention of my User I.D. partition is made whatwsoever, neither a sign-in windows is offered. It simply opens up already within the visitor's realm.

There is one folder named "User", which when clicked on, returns a small pop-up flag with the "Warning: Access Denied", which is surely where my own data is hidding. But no sign-in window is presented to access this partition.

Question: Does anybody know how to access I.D./password protected data stored in a Hard Disk Drive hooked to another computer as a secondary (slave) HDD ?

P.S.: When my HDD is hooked as the main (master) HDD to the working PC, after going thru the boot-up, the process is aborted at the point of showing for only an instant at the (Windows XP) sign-in window as it would in my PC.