Windows

You can convert a basic disk to a dynamic disk without having to reinstall - this is a one way move though.

Any MBR must contain at least 1Mb of space for the dynamic disk database - if this is not available, the conversion will fail. Do not convert a disk that contains multiple operating system installations.

System and boot partitions will only convert after restart - server could be down for a while.

If any of the following conditions occur, the conversion can fail after the computer restarts:
If you disconnect all existing dynamic disks while the computer is restarting.
If you replace a disk or set of disks to be converted while the computer is restarting. (Disk Management detects that the disk has changed and the conversion may fail.)
If you change the disk layout of a disk to be converted.
If the disk has I/O errors during the conversion.

In order to successfully convert a basic disk to a dynamic disk:

The disk must not be removable media. You cannot convert removable media devices to dynamic volumes. Removable media devices can contain only primary partitions.
The disk must not be in a portable computer. The sector size must be 512 bytes. Otherwise, you cannot convert a basic disk to a dynamic disk. You can use the chkdsk command to determine the disk's sector size.

Also, dynamic disks cannot be directly accessed by MS-DOS, Windows 95, Windows 98, Windows Millennium Edition, Windows NT, or Windows XP Home Edition