run disk cleanup and then Defragment the hard drive (right click on the drive in My Computer, select properties, then go to the tools tab)
open a command prompt windows and run a chkdsk /r on the problem drive.
More information would be helpful. what kind of hard drive? what kind of system? What OS?
How full is you hard drive?
How many running processes do you have?
What media player are you using?
also; try disabling the Indexing service and see if it improves. if not, right click on My Computer and select Manage, then select Device Manager, then select the problem hard drive located in Disk Drives. Right click on the drive and select properties then go to the Policy tab. Is disk caching enabled? If so, don't mess with it. If not, turn it on.