Apple's market value climbed past Microsoft's on Wednesday -- the first time that's happened in more than 20 years -- making it the biggest tech company in the world, according to Reuters.

At the end of the day, Apple's market value stood at around $222 billion, compared to Microsoft's $219 billion, reflecting the changing fortunes of the long-time rivals, as Apple's iPod, iPhone and now iPad have propelled the company into an enviable position.

Things are less than rosy for Microsoft, which hasn't enjoyed Apple's success in the mobile business or consumer market and is seeing increased competition on the software front from the likes of Google. But in New Dehli on Thursday, Microsoft CEO Steve Ballmer claimed not to be worried about Apple's gains, saying that he's focused on "what we should be doing to our product line, where do we go, how do we make products more innovative."

"It's a long game," added Ballmer, noting that while its competitors are tough, Microsoft is also "a very good competitor. We are executing very well and that is going to lead to great products and great success."

Ballmer, who is alternately portrayed in the media as a highly competent CEO or a crazed blowhard, took over Microsoft in 2000. During his reign, the company’s market cap has fallen from about $600 billion, though Ballmer can hardly be blamed for the dot-com bust and a massive recession.  But that didn’t stop a Forbes blogger from proposing Thursday that Bill Gates come back to the company to lead a Steve Jobs-esque resurgence. 

Apple's ascension to king of the tech hill comes on the heels of a management overhaul in Microsoft's entertainment and devices division, which includes Microsoft's mobile phone efforts, Xbox and Zune. On Tuesday, Microsoft announced that Robbie Bach, who had headed the unit since it was created in 2005, is stepping down this fall. Signaling Ballmer's desire to keep tight control over mobile, Bach won't be replaced. Instead, Andy Lees, head of mobile communications, and Don Mattrick, head of interactive entertainment, will report directly to Ballmer starting July 1.

Also out is J Allard, CTO of the unit and the man credited with designing the Xbox. More recently he was credited with creating the Courier tablet, a project that was recently scrapped. But in his farewell e-mail, posted to the Microsoft Web site, Allard didn't exactly sound bitter about his former employer: "We're the only high-tech company with the track record and self-confidence to reinvent ourselves as we have. If you want to change the world with technology, this is still the best tribe out there."

Reinvention may be a part of Microsoft, but the company's newly restructured entertainment and devices business never caught fire. The Wii and PS3 both outsell the Xbox; Zune is, well, Zune; and the company's smartphone OS market share stands at about 10 percent, well behind RIM, Google and Apple.

You can bet that Ballmer will be taking a very active interest in the unit as it prepares to launch Windows 7 Phone. Ballmer may pooh-pooh Google's obsession with mobile, but it's not much of a secret that for Microsoft to reassert itself over Apple, it will need to do considerably better in the mobile market.

Market value aside, by the way, Microsoft had higher revenues than Apple in the most recent quarter -- $14.5 billion, versus $13.5 billion.