Reformat?

I just got a external HD. Well, after looking around I been seeing people saying to reformat it to NTFS since FAT32 seem to have problems and stuff.

Is it really necessary?

If by "reformat", you mean "convert", then it's advisable. You won't get AIDS if you don't.

NTFS has several improvements over FAT such as improved support for metadata and the use of advanced data structures to improve performance, reliability and disk space utilization plus additional extensions such as security access control lists and file system journaling.