By and large, the S&P 500 Index (SNPINDEX:^GSPC) was able to shrug off weak earnings from the technology sector and the benchmark index even posted its fourth straight week of gains and finished at an all-time high on Friday. Not bad for a day that saw tens of billions of dollars disappear in a matter of hours from today's three biggest laggards alone. By the end of the day, the S&P had added 2 points, or 0.2%, to end at 1,692. The following three companies, however, lost their proverbial shirts. 

Advanced Micro Devices (NASDAQ:AMD) leads off this ignominious list after plummeting 13.2%. The chip maker reported earnings yesterday, and despite beating analyst expectations for the quarter, the shares were promptly downgraded by two analysts today. That's Wall Street for ya. To be fair, the company did swing to a loss and gross margins fell. Analysts were mostly concerned with AMD's gaming revenues moving forward.

By far the biggest name on today's list, however, is Microsoft (NASDAQ:MSFT), as shares in the software maker cratered 11.4%, the largest one-day slip shares have experienced since 2009. Like AMD, disappointing quarterly results prompted a flurry of analyst downgrades and price target decreases. What worried investors most were signs of a slumping Windows division, the cash cow and backbone of the business. The slow demise of PCs is starting to look like a very real and immediate threat to Microsoft's vitality.

Lastly, slot machine maker International Game Technology (NYSE:IGT) slumped 7.3%, due largely to negative analyst sentiment. Unlike AMD and Microsoft, IGT doesn't report quarterly results until next Tuesday, so the comments today were sure to attract the attention of some uneasy investors before official numbers come out. A Janney Capital Markets analyst said that the stock's been driven up to a point where it no longer offers newcomers an attractive entry point. On top of that, IGT is set to start losing market share, will see higher costs, and will be able to buy back less stock in the future, according to the report. 

Fool contributor John Divine has no position in any stocks mentioned. You can follow him on Twitter @divinebizkid and on Motley Fool CAPS @TMFDivine.

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