For three straight days, the stock market collapsed in the last hour of trading. On Friday, it merely swooned.

Until 3 p.m., things looked awful as investors drove the Dow Jones industrial average down nearly 700 points at one point - to below 8,000 for the first time in five years. Then the market did a U-turn, with the Dow surging nearly 900 points in less than 40 minutes. The rally fizzled in the last 20 minutes of trading, and the Dow closed down 1.5 percent - but that was a far cry from its 8 percent decline at the start of the trading day .

"We just don't see turnarounds like this," Howard Silverblatt, chief index analyst for Standard & Poor's, said of the late- afternoon rally. "These swings are enormous."

It was one of the wildest moves in stock market history and concluded the worst week in at least 75 years. The Dow and the broader Standard & Poor's 500 stock index both closed down 18 percent for the week. The Dow has never had a week that bad in its 133-year history. The S&P fell slightly more only twice before - in 1929 and 1933. It was the first time that the S&P has fallen by more than 1 percent for seven days in a row.

In the credit markets, conditions went from bad to worse. Borrowing costs for banks and companies jumped again as investors sought safety in Treasury bills, despite earlier signs that the government might take equity stakes in troubled companies to try and halt the credit crisis.

It was the worst single day for junk bonds ever, and the cost of borrowing shot up for even blue chip companies: IBM agreed to pay 8 percent interest on $4 billion of 30-year bonds, about twice the rate at which the federal government borrows money.

It was worse overseas on Friday. Britain's FTSE index ended below the 4,000 level for the first time in five years, Germany's DAX fell 7 percent, and France's CAC-40 finished down 7.7 percent. Japan's benchmark Nikkei 225 index fell 9.6 percent, also hitting a five- year low. For the week, the Nikkei lost nearly a quarter of its value. Russia's market never even opened.

On Friday evening, after a meeting of finance ministers and central bankers from the Group of Seven countries, Treasury Secretary Henry Paulson confirmed that the government will buy an ownership stake in a broad array of American banks for the first time since the Great Depression.

Separately, the United States and the globe's other industrial powers pledged to take "decisive action and use all available tools" to prevent a worldwide economic catastrophe.

"This is a period like none of us has ever seen before," Paulson said, adding that the government program to purchase stock in private U.S.