This sounds like a classic failing harddrive. My first recommendation is to BACK UP EVERYTHING right now to an external hard drive. If this is the case, you will likely be loosing bits of data here and there from any old files on your drive.

After you've backed up you have several options available to you

You can:

• Review windows event logs and look for any disk errors in them

• Run the disk manufacturers software diagnostics utility

• Attempt to fix any corrupted sectors on your harddrive using inbuilt tools for windows such as 'chkdsk'

• Download and use data recovery software (if needed)

  • additionally, if the files are critical you can send the drive to a data recovery specialist and they'll be able to recover files for you (although at quite a price). The rule of thumb here though is If the components in your drive are still functioning, you can recover the data yourself. If there is mechanical damage, send it to the pros

There are numerous causes for this, in the end though the best thing you can do is replace the harddrive after you've recovered as much data from it as possible.

Hope that helps, Cheers,