Though no USB Card reader installed, disabled USB, same problem.
Replaced the CD player by one of which I am sure it's working OK, same problem.
Inserted a brand new HD, same problem. PC keeps on hanging on the very same spot.
Fortunately I bought all the parts in the same PC shop, so I returned it and it will be tested in their workshop.
Thanks for trying to help me out. Have a great 2005!