** Please remember to include OS info **
Microsoft only has dynamic disks in Windows 2000/2003.
Optional in 2000 – preferred in 2003
Conversion is ONE-WAY! Going from basic to dynamic changes partition into volumes. To change back requires deleting volumes -BACKUP! BACKUP! BACKUP!
As stated in your query, you should be ok.
reference pp263-264 Windows Server 2003 Administrator’s Pocket Consultant