Probably a diagnostics partition.
I have an xp license I was going to put on a no os optiplex 790 I just purchased.  When getting to the partitions there is already a FAT32 2048MB partition on C.  When I went to delete it I got that it is a System partition.  I know there is no os to boot into so I was wondering if anyone knows what is on this partition before I think about deleting it.  Thanks.
No OS system partition