You can extend a simple volume on the same disk if the file system is NTFS.

A simple volume can be set to span other disks

NOTE: Both the above do NOT require a restart.

You can create a spanned volume on FAT or NTFS, but volumes created on FAT can not be extended or spanned further.

If the volume existed when the disk was still basic, it can NOT be extended or spanned. You receive:

The selected volume was originally created on a basic disk and cannot be extended. Only volumes originally created on dynamic disks can be extended.

NOTE: You can back up, delete and re-create it on a dynamic disk and restore the data.