You must have ignored the warning that it was about to convert to Dynamic, which is meant for partitions to span multiple HD's.
You can have 3 Primary and as many Logical subpartitions as you want on each MBR HD, or four Primaries - any more than that will need to be converted to Logical partitions first.
You can do this without destroying your data by using free Partition Wizard bootable CD version 4.2 which was the last version in which this feature is free. Download this zip file, extract the ISO inside and burn to CD using Windows Image Burner or ImgBurn: pw422.zip ISO - Windows Live
Follow this video tutorial to do the conversion: How to convert dynamic disk to basic disk with Partition Wizard?