I am using a partitioned hard disk (partitions C, D, E) on a WindowsXP Pro system. C is the system partition and running out of space now (only 200 Mb left!). E, on the other hand, is almost empty. So I'd like to hand over some of the unused space on E to my system partition C, without loosing any data on C.
However, the windows disk management tool tells me that it cannot

extend the current system partition. How to proceed?