They actually made some improvement with Vista's Disk Management now seeing the ability to shrink or grow secondary partitions not the one Windows is being loaded from. For that you need to boot up with a full install version disk to use the optional drive tools found there or a separate partitioning tool either retail or the Linux tool GParted live for cd.
Have a cd or dvd burner and a blank cd-r? For the price of a blank disk and a little time you can grab the free Linux tool for expanding the current primary before you start seeing the "out of drive space" or "out of memory" errors when there's no longer enougn drive space for the paging file used for virtual memory.
First review the information along with screen shots to get familiar with the tool itself. GPARTED DOCUMENTATION - GENERALITIES
The main download page for the cd iso images is seen at SourceForge.net: Files
For those who lack any experience or plans on running any Linux distros I generally refer them to the two platform independent releases of GParted for making things easier when working with MS type partitions. They still haven't released any newer releases but continue to see the two 0.3.3.0 and 0.3.2.0 versions once you scroll half way down the page there.