More on the topic: http://mypkb.wordpress.com/2007/03/28/how-to-non-destructively-convert-dynamic-disks-to-basic-disks/ http://support.microsoft.com/kb/913964
The success rate is close enough to 100% so long as you don't resize or move the partition boundaries, but there's always that one machine out there that just doesn't work with something no matter how many thousands of hours the developers put in, nor what the developers do to avoid it.
It gets worse as these same people don't provide any feedback to the developers giving them the free and open software (in this case) in the first place.