Basic storage involves dividing a disk into primary and extended partitions.
To perform a downgrade, data on the dynamic disk must first be backed up onto some other storage device.
Finally, data from the backup must be copied back over to the newly re-formatted basic disk.
Thus a CompactFlash (CF) card capable of true IDE mode connected to a PC running Windows through an IDE port or a USB to ATA bridge, a mobile HDD enclosure case for instance, would get this reservation in contrast to one being connected through a normal USB card reader or a passive 16-bit CF to PCMCIA adapter where it does not deserve this reservation.
In Windows XP, spanned volume can use a maximum of 32 physical disks.
One cylinder depending on drive geometry and translation can be up to 8 MB (to be precise, 512 bytes/sector × 63 sectors/head × 255 heads/cylinder = 8225280 bytes = 7.844 MiB) which account for a remaining 8 MB free space once Windows setup is used to create a partition.
Coincidentally, Solaris 11 leaves exactly this amount of space at the beginning of a disk.
Disk Management in Windows Vista creates partitions according to a 1-MB alignment boundary, ignoring the previous conventions called "drive geometry" or "CHS".