HD Tune often displays nonsensical results, eg negative counts.
Either of the following will produce better output.
HD Sentinel (DOS / Windows / Linux):http://www.hdsentinel.com/
HDDScan for Windows:http://hddscan.com/
See this article for an explanation of the SMART attributes:http://en.wikipedia.org/wiki/S.M.A.R.T.
The "life time write from host" attribute is a count of the total number of sectors written to the drive by your PC during the drive's lifetime, ie Total LBAs Written.