You can convert a basic disk to dynamic without losing data (as long as there is enough free space on the drive to create the partition record database partition at the end of the drive).

Just go to XP's Disk Management, right click on the drive's volume label to the left of the partition display (normally shown as Disk0, Disk1 etc..) and select convert to dynamic.

However you can't convert a dynamic disk back to basic disk without first wiping and re-creating the volume, as it requires the repartitioning of the entire disk (because dynamic disk partitioning is proprietary), so all data and existing partitions would be lost.

Remember that OS's before Windows 2000 cannot access dynamic disks. And non Windows OS's such as Linux cannot access them either. They are also not supported by XP Home or portable computers.

It is annoying how M$ changed the way disk partitioning worked since Windows 2000. Before that you could setup a stripe, mirror, or spanned set using basic disks. But now you have to convert the drives to dynamic before this is possible. I suppose the more advanced technology used by dynamic disks is more robust and better.