Some analysts have predicted that despite Microsoft's intention to spend half a billion dollars marketing Vista, conversions from XP .

Statistics for the first week of February -- Vista officially launched Jan. 30 -- were mixed. Current Analysis found sales of PCs -- with Vista preinstalled -- were up 173 percent from the week before. PC sales were also up 67 percent from the same time frame in 2006. But Current Analysis itself pointed out that the sales leaps were exaggerated partly by slowing sales as retailers and OEMs wound down their XP-based inventory.

By comparison, NPD Group Inc. found that first-week sales of boxed copies of Vista were down 60 percent compared with first-week boxed copies of Windows XP five years earlier.

Neither group has released statistics of Vista sales in subsequent weeks, though NPD analyst Chris Swenson is expected to release first-month retail sales of the new OS soon.