Usually it's harmless, but anyway can be easily fixed in Linux with a fdisk utility: just start fdisk with a HDD device as an argument (e. g.:
fdisk /dev/sdb), then sequentially press 'x', 'f' and 'w' keys, and finally reboot your system (for the changes to take effect).
- you can do this from a some sort of Live CD / Live USB environment;
please don't try this on a running production system;
- partition numbers get changed, and some OS's sometimes don't like this;
- the partition table can get corrupted -- make backups prior to any experiments.
Here is a sample output log:
# fdisk /dev/sdb Welcome to fdisk (util-linux 2.21.2). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Command (m for help): m Command action a toggle a bootable flag b edit bsd disklabel c toggle the dos compatibility flag d delete a partition l list known partition types m print this menu n add a new partition o create a new empty DOS partition table p print the partition table q quit without saving changes s create a new empty Sun disklabel t change a partition's system id u change display/entry units v verify the partition table w write table to disk and exit x extra functionality (experts only) Command (m for help): x Expert command (m for help): m Command action b move beginning of data in a partition c change number of cylinders d print the raw data in the partition table e list extended partitions f fix partition order g create an IRIX (SGI) partition table h change number of heads i change the disk identifier m print this menu p print the partition table q quit without saving changes r return to main menu s change number of sectors/track v verify the partition table w write table to disk and exit Expert command (m for help): f Done. Expert command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.