Microsoft CEO Steve Ballmer is questioning rival Oracle's decision to acquire server manufacturer Sun Microsystems, claiming he has "no idea" why Larry Ellison's company would make such a move.

"I have no idea why a software company would buy a hardware company," Ballmer said Wednesday. Speaking to the American Chamber of Commerce in Cairo, Egypt, Ballmer added that Microsoft doesn't "want to buy any hardware companies," the Reuters news agency reported.

Ballmer also said Microsoft isn't interested in acquiring Yahoo.

Ballmer may have good reason to puzzle over Oracle's planned $7.4 billion buyout of Sun. The move comes at a time when the market for big computing iron -- such as Sun's flagship Sparc enterprise servers -- has all but dried up.

Tech bellwether IBM earlier this week reported that System Z mainframe sales dropped 19% year over year in the first quarter, while sales of commodity-style System X servers plunged 27%. Midrange System p servers, which run the Linux and AIX operating systems, declined 2%. Overall, IBM's Systems and Technology Group reported a 23% drop in sales, to $3.2 billion.

On the other hand, Ballmer may be simply looking to downplay the fact that the Sun deal will likely make Oracle a stronger player in the business software market.

Sun controls a number of key, widely used assets, including the Solaris operating system, the open source MySQL database -- which boasts more than 11 million installations -- and the Java programming language, which has become a standard for Web application development.

In announcing the deal Monday, Ellison said combining those offerings with Oracle's database and back-office automation applications would help businesses cut computing costs will increasing efficiency. "Our customers benefit as their system integration costs do down while system performance, reliability, and security go up," said Ellison.