Hang on one of dual boot systems

I have a w2k-sp4/XP-sp1 dual boot pc (P4 2.8 Ghz Asus P4P800). I boot into W2k with no problem at all. On the other hand, when selecting XP, the boot process hangs when it reaches the Windows logo against a blue background.

I had a look at various forums on this topic and tried the solutions suggested to no avail.

Going into Safe mode comes up with exactly the same result, regardless of the options selected.

I ran Avast against the XP partition from the w2k system. No virus found.

I replaced the faulty XP partition by an early operational copy from a USB disk.

I replaced the disk containing XP by a brand new one.

I ran XP Install-Repair with an XP-SP2 cd-rom. When the process reached "34 minutes remaining", a black screen appeared. The process went on for two or three minutes and then stopped. I ran the Repair once more with the same result.

It's interesting to note that for the past few years, I have had no problem at all with W2k (it's my working OS) while, during the same period, I had to re-install XP several times.