A failed Reallocated Sector count is bad. I would get any important info off the drive and onto a external drive as quickly as possible before doing the test. Even doing a Seatools test can stress the drive to a point where you cannot get your info off. Seatools for Windows will work for testing the drive. Seatools for Dos can try and repair sectors.
Edit: From Wiki
Reallocated Sector Count
Count of reallocated sectors. When the hard drive finds a read/write/verification error, it marks that sector as "reallocated" and transfers data to a special reserved area (spare area). This process is also known as remapping, and reallocated sectors are called "remaps". The raw value normally represents a count of the bad sectors that have been found and remapped. Thus, the higher the attribute value, the more sectors the drive has had to reallocate. This allows a drive with bad sectors to continue operation; however, a drive which has had any reallocations at all is significantly more likely to fail in the near future. While primarily used as a metric of the life expectancy of the drive, this number also affects performance. As the count of reallocated sectors increases, the read/write speed tends to become worse because the drive head is forced to seek to the reserved area whenever a remap is accessed. If sequential access speed is critical, the remapped sectors can be manually marked as bad blocks in the file system in order to prevent their use.
Edited by JohnC_21, 16 November 2014 - 10:50 AM.