Microsoft’s letdown with Windows Vista operating system seems to have picked up some pace. Approximately 35% of the PC’s produced to run the Windows Vista have been downgraded to XP according to a recent survey.

The study carried out by Devil Mountain Software, a software development company, included more than 3,000 PCs. Those who managed the survey concluded that one in three computers had either been downgraded by producers or by their customers after the purchase.

Ironically, one of the good things about Windows Vista is that it includes downgrade rights, which implies that if one has a copy of XP, it can be installed on the PC without extra charge.

Vista’s vendors probably wanted to be more flexible with this version of the operating system, but, to their surprise, more than 35% of the enterprise customers actually used the downgrade rights policy, the study shows. Considering the fact that the info comes from a system performance monitoring tool that users can chose whether to install on their PC or not and can’t monitor those who changed Vista with Linux, the 35% could be on the low side.

Microsoft ended most Windows XP sales on June 30th.

The study did not mention any reasons why customers are using the downgrade option so frequent. However, the news about the survey’s findings slows down Microsoft’s expectations of stronger Vista sales in the short term. The downgrade option will phase out in a few months and then customers won’t have the alternative anymore.

Microsoft is currently making efforts to boost the interest in its latest operating system – Windows 7. Windows’s head, Steven Sinofsky, has started a blog about Windows 7 in an attempt to create a positive image of the new operating system which unfortunately looks pretty much like Vista 2.0.