Can only access WD ext HD for a while before computer can no longer see it

I’ve been using my WD 750 GB ext. hard drive for almost a couple years now and just yesterday it (or my comp…) have begun acting up.  I store all my music for iTunes on the ext HD, so I first noticed there was a problem last night when attempting to open files on iTunes but they couldn’t be located.  I opened “My Computer” and there was just a generic icon displayed for my ext HD, so I opened it and could see all the icons for everything but was unable to open anything.  I did a complete system reboot, and when I opened iTunes again it saw all my music; however, when I came back an hour later it could no longer locate some of the music and I couldn’t open anything on the ext hd again.  Any ideas why this is occurring?  Is the ext HD about to ■■■■ out on me or is something on my computer preventing it from communicating properly?

Thanks for you help in advance,

Seth

something wroing with HD or case :confused: