Dissatisfaction with the original version of Windows Vista has prompted an overwhelming majority of users to download and install the operating system's first service pack, according to a group of researchers.

Industry watchers at Devil Mountain Software said 86% of Vista users had installed SP1 as of the end of July, compared to the 69% of Vista users that were running SP1 at the end of April.

"There was tremendous pent up demand for Vista SP1," said the researchers, in a blog post Thursday.

The high adoption rate is "either due to customer dissatisfaction with the product or because users were convinced of its benefits from all of the media hype surrounding its release," wrote the research team.

Microsoft made Vista SP1 available as a free download from its Web site in March. It's also been slipstreamed into boxed versions of Windows Vista available from Amazon.com and other retailers.

Vista SP1 contains a number of features designed to enhance the operating system's speed, performance, and stability -- all subjects of frequent user complaints.

Among other things, it offers a patch that will allow users to run the BitLocker encryption tool on multiple hard drives. It also improves the speed at which the OS wakes up from "hibernate" mode.

SP1 will also remove from Vista the so-called Kill Switch -- a feature that deactivated key components of the OS if Microsoft detected users were not running a properly licensed copy.

The feature was plagued by false alarms that flagged thousands of legitimate Vista users as software pirates.

As for Windows XP, Devil Mountain Software reports less than half of the older operating system's users have upgraded to the recently released Service Pack 3. "Most likely because, overall, the majority of users are quite happy with Windows XP + Service Pack 2," said the researchers, who noted they also found "a handful" of users still running Windows XP SP1.