The system requirements involved in upgrading to Microsoft's Windows Vista operating system remain a problem for many IT departments. But they can be magnified at mid-market companies, because of smaller budgets and smaller staffs, with tech vets who may be resistant to change.

Unlike small businesses, mid-market companies don't solely use store-bought mainstream applications that integrate smoothly with Vista. They tend to use mainstream apps along with older and internally-customized applications that are more likely to butt heads with Vista.

And then there are the hardware requirements. When Vista was released, Microsoft advised that businesses run Vista on computers with at least 40GB of storage, 1GB of memory and a 1GHz 32- or 64-bit processor. IT managers in the mid-market continue to grumble that Vista requires more modern hardware than they want, need or can afford.

"Our decision [to stay with Windows XP] was initially based on our installed hardware base," says Mark Horste, IT Director at Centers for Dialysis Care, a midsize health care facility in Cleveland.

"Our purchasing cycle for PC and thin client platforms favor consistency and cost effectiveness," Horste says. "Early tests of Windows Vista indicated it simply would not run fast enough on the majority of systems on our network. Windows XP has proven to be a stable and adequately secure operating system for our needs."

Smaller companies have been quicker to upgrade to Vista than the mid-market, to date. Still, Al Gillen, a research vice president at IDC, says that signs show that the mid-market is coming around on Vista.

"Our research shows that the mid-market is warming up to Vista and will continue to do so in 2009."

A Gradual Warm-Up to Vista Ahead?

Bolstering IDC's predictions, there have been some incremental victories for Vista over the past few months. In August, Forrester research data showed that Vista deployments were finally ramping up at enterprises, and that Vista migrations were coming from Windows XP machines, whereas previously, most were coming from Windows 2000.

On Monday, Microsoft reported that Windows gained market share for the second time in three months, with Vista increasing its market share 0.96 percent last month.

The release of Vista Service Pack 1 in March and a slow—albeit very slow—shift in the public's negative views of Vista are two factors that may be giving mid-market IT managers some comfort.

But the Vista adoption story is a complicated one. And for every positive report about Vista adoption, there's one brimming with bad news right around the corner.