A majority of desktops in enterprise companies today won't be ready for a Vista upgrade, at least not without quite a bit of work.

So say the results of a recent survey conducted by software-as-a-service desktop management vendor Everdream. The company expects to release the results next week.

Everdream conducted the survey by running reports on existing system attributes against Microsoft's recommended system requirements across 145,000 desktops in 1,000 of Everdream's installed base of customers. The results show that about 80% of machines did not meet at least one of Microsoft's four criteria for optimal systems targeted for Vista upgrades.

"The cost of getting computers into compliance with Microsoft's requirements will likely be a huge obstacle to Vista adoption. IT managers will need to plan the work that needs to be done before they can upgrade to Vista," says Ed Mueller, Everdream chief marketing officer. "Understanding the requirements they aren’t meeting yet will be instrumental in making a move to Vista."

The operating system vendor defined recommended requirements for "Pentium-ready PCs" as 1GB of RAM, 1 GHz processor, 40GB hard drive and 15GB free hard drive space. Microsoft also defined minimum requirements against which Everdream also tested the desktops. Microsoft requires machines to have a minimum of 512MB of RAM, 800 Mhz microprocessor, 20GB hard drive and 15GB of free hard drive space.

Among the challenges Everdream notes in future Vista upgrades are evaluating and identifying which machines don't meet the recommended hardware requirements, fixing software incompatibilities and backing up data from machines before the upgrade.

The survey shows the biggest hurdle companies will face upgrading to Vista is the amount of RAM on desktops. While Microsoft requires a baseline of 512MB of RAM, the company recommends 1GB -- a requirement just 30% of the desktops met.

When compared against the recommended requirements, about 70% of machines don't have the required RAM, more than 60% don't have the required hard drive, about 20% don't have the required free hard drive space and about 7% don't have the required processor speed. According to Everdream, more than 90% of companies have at least one machine that doesn't measure up to Microsoft's recommendations.