in my opinion ... <title> " download windos vista " ( more effective ) adsense > here disc> blha blha blha = download link ( just waste, but sure you have to blha blha here..) what you think earnigs from this way ?
On my software download project, Adsense did little content-relevant until I added some automatically-generated (as in: generated from a uniqe content text describing the download) meta-keywords and meta-description. CTR skyrocketed as well.
They may have some impact because they could determine the type of ads that pop up, but the content itself is the most important factor.
the biggest mistake is, that many wbmasters don' t target for only one keyphrase, but for many. This is a very important factor to stay narrow.