Hi
I started to suffer from the lightningsand.cfd message at start up. And I have cleared it.
At first I ran chkdsk from the Run box. It only ran what seemed like a short "readonly" version. And didn't clear it.
Then via control panel and disc management I found a version that runs at restart. It took a long time but it seemed to clear it.
Also it may sound silly to remind people but the problem was on my external drive, and chkdsk uses C drive as default so make sure you select the right drive relating to the drive in the error message.
Hope this helps others.
Chris