System disk check failed

Hello, I recently moved to Ubuntu 8.04, everything seems to go fine, now there is a problem. My system says that it needs to check hard disk, when it checks the check fails at 24% and it asks me to do fcsk manually. When I type fcsk it says the command is not found.

Some of my folders in Music directory are automatically getting locked. I had this same problem before (7.04). Is there any solution? Could it be a fault / bad sector in hard disk?

I am great fan of Ubuntu and don't want to miss it.