|Yeah, I was wondering that too.|
Not sure what you mean by 5541 drives from a 64 or do you mean model 1541 drives from a commodore 64? Those were single side floppy drives meaning they could only read one side of the disk. The notch in the side of 5.25 disks enabled it to be written to--it didn't designate a low or high density disk. If you covered the notch with tape you made it read-only. With single sided disks you could usually flip them over and use the other side. In that case you had to make a notch in the other side of the disk in order to write to it.
Most of the time you could write to both sides of a single sided disk but the manufacturer only guaranteed one side to be good.
High and low density disks looked exactly alike except low density ones had a colored ring around their center hub. Sometimes you could format a low density disk to a high density format but that wasn't a good idea as they often lost their format.
I don't know if XP will work with any 5.25 drive. I know XP is only supposed to be able to format 1.44 disks but the XP format command has the f:size option to format to other densities. If XP can work with those older disks I know they won't be able to read the commodore format on them so you'd have to format them and reuse them as blank.
I'm not sure what else, if anything, you're asking about.