Before you do anything...you need to find out why that second partition exists.
Chances are, it wasn't created just to be a fancy decoration in My Computer.
You might check your owner's manual.
Then...if you still want to play with partition management...you may want to look at this free tool: EASEUS Partition Master is a magic partition manager software for Windows 2000-XP-Vista-2003- - http://www.partition-tool.com/
Note that this software will not allow a simple merge of partitions. But it will allow you to resize, move, etc.
One way to eliminate one of the partitions: Move any data (on the unwanted partition) that you want to the other partition, delete the unwanted partition, then increase the size of the remaining partition.
FWIW: I believe that you are actually better off with 2 partitions if you only have 1 hard drive. The two partitions would tend to lessen the chances of total loss
of files, in the event that the file system gets botched or the disk has mechanical problems.