to run Scandisk - that will reveal any errors on the drive structure.
The message is telling him/her quite plainly that the drive may be about to fail, and I would have thought that the solution is pretty clear:
1. Immediately back up all data files.
2. Back up the partition with the Windows files on it.
A neat way of doing this is to buy the new hard drive (which you're going to have to do anyway) and install it in the computer as a slave. Partition the drive, and then, using Windows Explorer, drag and drop the entire contents of the Windows partition onto the new drive. Put the files into any partition except C: Now drag the data files over in the same fashion, but put them into a different partition. Make sure that you create a Windows startup disk if you don't already have one.
Now you have a nice new drive with all your files in place. Ditch the old drive, install the new drive as the master and start the computer with the startup disk in the floppy drive. Select the option to start the computer with a command prompt, and at the C: prompt type the drive letter that contains the Windows files followed by a colon. Hit the enter key, type: setup.exe and hit the enter key again. This should start the Windows installer.