By Aidan Malley

Published: 07:50 PM EST

Microsoft touted the breakneck pace of Windows Vista sales on Monday, pointing to the dramatic improvement over XP's early figures and creating an imposing benchmark for Mac OS X Leopard's initial success.

The Redmond company was keen to report the positive uptake on its new operating system, claiming that over 20 million copies had traded hands worldwide in the month since the official Vista release on January 30th.

Those figures easily doubled the numbers managed by Windows XP, which itself had record sales of 17 million units in the two months after its release in October 2001. Putting the company's success in perspective, however, Windows marketing director Bill Mannion noted that the results were good but not out of line with his employer's goals.

"It's a little bit better than what we were expecting," he said.

Microsoft's new statistics seemingly canceled out its earlier cautious stance, which had been pragmatic at best: just last month, company CEO Steve Ballmer had labeled investment groups' predictions "optimistic" and warned that Vista was primarily the firm's way of sustaining marketshare.

Nevertheless, the sales will prove a potential barrier to Apple's own quest for a greater piece of the market. Upon its release in 2005, Mac OS X Tiger's success managed only a tenth of its Windows XP rival, selling 2 million copies in its first four weeks. Roughly 7 million copies were sold in the year as a whole.

Further emphasizing the challenges faced by Apple are the company's demographics. The computer maker reported 19 million active users of Mac OS X at last year's WWDC gathering -- meaning that Apple's entire user base could fit into less than a single month of Microsoft's most recent OS customers. A reported swelling of the former's ranks to 22 million this month, according to analysts' estimates, would still be overshadowed by Windows.

Without immediate evidence of Vista floundering in its intial sales, Apple's long-term success will therefore depend more than ever on Mac OS X Leopard's release in the spring to boost its stake in the computer business, possibly riding the coattails of Vista towards its own sales spike.

"We like how Vista has established a 'hardware upgrade mindset' among PC users," said ThinkEquity analyst Jonathan Hoopes earlier this month. "And we expect Apple CPU unit shipments to benefit from Vista tailwinds [and] the release of Leopard."