How to tell if your HD has bad clusters/sectors?

[Muse]

I've seen several posts lately with people saying they have had bad clusters on a HD. How can you tell if your HDs are getting bad clusters. My understanding (please correct me if I'm wrong) is that a modern HD has disk space set aside as a sort of buffer against bad cluster formation. Thus, when the OS behind the scenes determines that a cluster (or is it sector?) is bad or going bad it automatically moves the data to this "buffer" and marks the bad/questionable sector as bad. So, if this is indeed the case (as I understand it), you won't know when an area of the disk goes bad until you run out of the set-aside space. Once you run out of this space the OS actually informs you that you have bad sectors. By that time, your disk is very questionable and probably on the way out and you should RMA the thing if it's within warranty. Am I right here or no?

 

[Evadman]

You run scandisk or the equivelent.