Do you mean "Trying to recover allocation unit..."?
Sounds to me like you've encountered bad sectors while formating your drive. How old is it? What make/model? Here is a snippet from a website on this type of error:
"If FORMAT stutters during its progress and says it is trying to "recover an allocation unit", chances are that the drive has sustained some physical damage and has bad sectors. If you were out of the room and missed this, a summary of the drive, including of any bad sectors, will be displayed at the end of the format process.
To look further at any bad sectors, use the SCANDISK utility, and run a surface scan. If there are only one or two bad sectors, and their location is apparently random, it's likely the drive has been damaged. However if you find large numbers of bad sectors, either in some sort of a pattern, or all starting at one point, it is possible that the drive has not been properly set up in CMOS.
Normally the presence of bad sectors is an indication that a drive is 'on it's way out'. However if the bad area is not too big, and is located toward the end, you might consider repartitioning the drive to use just that part of the drive that is unaffected. This practice is not recommended for a system where data integrity is important."