Problem is that when I plug the disk on the troubled Windows machine and go to Logical disk manager to format it, I discover that the partition appears as a GPT protective partition and you cannot do anything to it.
EFI label. EFI adds support for GUID partition tables, and that (partially) explained the behavior of the Logical disk manager. I didn't even imagine that Windows XP would know about EFI of GUID partitions tables and I understand why it didn't let me touch that disk. What I didn't know was how to clean the disk to be able to format it with NTFS. Fortunately, Google always helps who knows what to search, and I discovered about the existence of a command line utility called diskpart. With diskpart it was easy to clean the disk and format it again. Instructions are straightforward:
- open a command prompt
- launch diskpart
- list disks with the list disk command
- select the disk you want to clean with the select disk command
- clean the disk with the clean command