As far as I am concerned the BEST way is to do a complete re installation of the operating system using the original installation disc and remove the unwanted partition at that time.

Others in here will argue about using partition magic or other partitioning software. While these programs can do this, it is a toss up (50/50 chance) as to whether it destroys some critical operating system component or not and then you will be forced into re-formatting / re-installation

Resizing the drive from larger to smaller is a different thing all together and is done relatively safe. When you make it larger by combining partitions is when the trouble starts.

If you have a decent sized drive.... I suggest that you format the other partition to clean it up. Then make that a storage partition by moving the MY documents folder to that partition. Then all your personal files will be separated in case of operating system failure. This also clears up space on "C" drive.