This is the answer I copy from Yahoo... just to share! I think this comment is quite reasonable.
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Do you get the imminent failure message shortly after you turn on your computer (ie before booting into Windows) or after Windows starts booting? If it's before then it's a SMART error message. SMART stands for Self-Monitoring Analysis and Reporting Technology which is used to warn the user of hard drive problems giving you time to back up your files before the drive fails completely. If this is your situation, get a new hard drive immediately. Do not pass Go, do not collect $200.00 and do not run any check disk utilities at this point as they can stress your hard drive right into total failure.
If you get the imminent failure message after booting into Windows it might be spyware. In that case the other suggestions on here should help.