It has nothing to do with the other partition and it will not destroy any data. All it does is convert from fat to ntfs on the partition you specify (the above command is for C: drive - if that's not the drive you want to convert, replace the letter C with the correct partition letter).
New Technology File System. It offers a lot of security and stability features not found in previous files systems. Fat32 is actually an 'enhanced' Fat16. Here's a pretty good non-technical article about it.
By the way Nobby, you need to recognize that the conversion to NTFS is a one way process. Once you've converted, you cannot change back to FAT without either reformatting (which means you'd erase all data on the drive) or using a 3rd party utility such as Partition Magic 7.0 (which can perform the task non-destructively).
I'm not suggesting you would want to go back, just explaining the situation.
Ep, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS