Dynamic disk and volume management has been provided to Microsoft by VERITAS Software Corporation. That means it supports some advanced volume management techniques.
People often need to shrink a volume, just so they can install that new release of Solaris or OpenBSD. But to do that, they need some free unallocated disk space they can create a primary partition from (in case of Solaris and BSD, which need to be installed on primary partitions).
With older versions of Windows people would use GNU Parted (QtParted, gParted front-ends), Partition Magic or FIPS. Now you can just use diskpart to safely resize NTFSv5.
Let's assume we want to shrink a volume by 80GB. Just open a command prompt and type:
select volume NUMBER
shrink desired 81920
You can, of course, just use the graphical interface available as a mmc snap-in (start - run - diskmgmt.msc).
Now you can use the available disk space to create a primary partition for your new operating system, and dual-boot it :-).