registers for your drive with a tool like SMARTReporter, you should see an entry with ID number 05 and title 'Reallocated Sectors Count'. I don't know when it started but some time back the ability to remap a bad sector was merged into the firmware of the hard drive. I doubt you will find any software tools to 'fix' bad blocks, at least for recent hardware. What type of a Mac and what type of hard drive are you having problems with?
I don't know of any tool that will do a surface scan and fix the bad blocks too.
