Microsoft Corp. (MSFT) said Friday it increased its ongoing share buyback plan by about $16.2 billion, almost doubling its repurchase authorization to $36.2 billion through June 30, 2011.

The world's largest software company has been sitting on a huge pile of cash that it didn't think it needed immediately for things like legal expenses and acquisitions. As of June 30, the end of its fiscal year, Microsoft had $34.16 billion in cash and short-term investments.

In July, the company said it planned to repurchase as much as $20 billion worth of shares by Aug. 17 in a tender offer. However, the Redmond, Wash.-based company said Friday it will only be buying about $3.8 billion worth of shares in that "Dutch Auction." That's about 155 million shares, or 1.5 percent of the company's stock, at $24.75 a share.

But in July, Microsoft also said its board had authorized it to spend as much as $20 billion on more traditional stock repurchases by June 2011, and that is the program it increased on Friday. It also said then it had already completed a previously announced $30 billion stock repurchase program.

The July buyback announcements came on the heels of a 24 percent drop in fourth-quarter earnings to $2.83 billion, or 28 cents per share, despite a 16 percent increase in revenue to $11.8 billion. The company had warned of the lower earnings in April, saying the drop was due to the company's plans to boost research and development spending in areas where it is not dominant.

Stock buybacks generally boost a company's share price because they lower the number of outstanding shares available on the market.

Microsoft shares rose 31 cents, or 1.3 percent, to $25.01 in early trading on the Nasdaq.