Can't Defrag HD

i have a seagate 320gb HD (ST3320620AS)... When i try to defrag it, it defrags some of the HD and then it just stops and says defrag was unable defrag some files in this volume.. theres a big red section thats still fragmented.. The HD is brand new.. anyone know what the problem could be?

Probably locked files. Running any kind of file transfer programs (P2P) or the like?

May want to check for some offline defrag utilities.

Umm, maybe an obvious question, but is the hdd full? If my hdd has only 10-15% free space, I find that no matter how many times I defrag I still have a couple fragmented files. I think it comes from the fact that there isnt enough room to move files.