What is the balloon actually telling you? Unfortunately, ".... telling me something is corrupt and unreadable ...." isn't really enough to go on.
To run CHKDSK you open My Computer, right click on the drive and select "Properties". In the box that opens click on the "Tools" tab. The top item on the page is called "Error Checking" - click on the button marked "Check Now" and click "Okay" to any warnings it pops up. "Okay" your way out. Reboot the machine and let it run the error check on startup (it will do it automatically for you). If that fixes the problem then just let us know. Otherwise we will need a bit more info as I asked above.
"Hardware: the parts of a computer that can be kicked!"
Please don't send me PM's for support. Post in the forums for everyone to benefit.