You probably have defined too many partitions on your disk, which is why it got converted to dynamic.
First, get a partition manager that is bootable from CD, such as GParted or Partition Logic, and delete the partition that you added.
Next, TestDisk will allow you to backup your data and, if you let it rewrite the partition structure, it will convert your dynamic disk to a basic disk without touching the data.
For a detailed description on using TestDisk see :
How to non-destructively convert dynamic disks to basic disks.
Just be careful : The smallest mistake could cost you the entire hard disk, requiring re-installing everything again.