Yahoo! says it spent (US)$79 million last year fighting off the then-unwelcome overtures by Microsoft (MS) to take over the financially troubled company’s search business.

The figures were buried in a mandatory annual report by Yahoo! to the U.S. Securities and Exchange Commission (SEC), which monitors the activities of all publicly traded corporations in the U.S.

In a nutshell, Yahoo! spend millions on outside financial and strategic advisers to fight off two threats.

The first, was the unsolicited offer from MS to buy Yahoo’s search business for (US)$33 per share of Yahoo! stock. Then CEO Jerry Yang rebuffed the MS offer.

Then, Yahoo! mega-investor Carl Ichan tried to take over the company, which he felt was being ill-managed, in a proxy fight.

Finally, when Yahoo attempted to make a friendly search deal with Google, it hired more outside advisers.

Ultimately, Yang resigned as Yahoo!’s CEO, Ichan stepped back, MS backed off and Google bailed on the search deal when its own advisers warned that the proposed arrangement could lay Google open to onerous anti-trust challenges. And, most recently, Yahoo! has been openly courting MS — the only player able or likely to make a rescue deal with the once mighty Internet search pioneer.

Bottom line: Yahoo! Spent almost (US)$80 million and ended up right back where it started from.

For those with the interest, ability and stamina to read dry financial reports, the entire Yahoo! filing can be viewed online at the SEC Web site.