|No, that was the first thing i tried. You can't assign a drive letter to a _system_ partition through disk management tool. It will say: "windows can't change drive letter of a system partition".|
Same thing applies to the diskpart utility:
From the microsoft support article you provided:
assign [[letter=l]/[mount=path]] [noerr]
Use the assign command to assign a letter or mount point to the current in-focus volume.
The drive letter assignment is blocked on the system, boot, or paging volumes.
So, no go.
-System is operational now. It boots correctly and everything works fine. Only problem if we can call it, is that partition letter is D: (with no C: partition) and I think this gives problems or confuses any application trying to work at boot time like for example acronis disk director. (creating unrecoverable crashes - bsods, only recoverable by xp cd recover installation). What i am sensing is that for a small fraction of time, at boot time, windows refers to the first partition of the first drive, as C:, no matter what you called it, and then, as soon the system starts to load, it gets instructed to call it D: (or any other letter you chose).
And I think this is the mechanism that should be investigated on, to get those application that work at boot time to behave correctly, in the case a D: partition is present and a C: is not.
For I really think this is not a personal issue of my computer, but will affect anybody with the same partition configuration. Or maybe other non standard partition configurations as well.
Tools which work at boot time, like Acronis Disk Director or Partition Magic, from what i know, are the only ones which can change a letter of a windows _system_ partition because apart from changing its letter, they also need to go through the system, i think, and change all the references from (i.e.) D: to C: (xp registry as well?).