With the PC market still struggling, it's no shock that Microsoft's (NASDAQ: MSFT) fiscal fourth-quarter earnings left investors wanting more. Total revenue was $19.9 billion, which translated into net income of $5 billion, or $0.59 per share. A year ago, the company had posted its first net loss as a public company of $492 million, primarily due to the massive aQuantive writedown.

This time around, it was a growing inventory of Surface RT tablets that had to suffer an inventory charge to the tune of $900 million. The Surface RT inventory adjustments hurt Microsoft's bottom line by $0.07 per share. Still, even without the charge, Microsoft would have fallen short of the $0.75 per share consensus estimate that investors were hoping for.

Investors might remember when BlackBerry took a similar charge in 2011 from its glut of unsold PlayBooks. The Canadian company took a $485 million charge just months after launching its seven-inch tablet. Microsoft now feels BlackBerry's pain.

That's nearly $1 billion that Microsoft is eating as a result of slow Surface RT sales, and was the driving factor for the precipitous rise in cost of revenue that subsequently hurt gross margins. Gross profitability fell from 77% a year ago, to 72% last quarter.

Microsoft has made numerous moves so far this year to get Surface RT units moving. In June, the company began offering the device to educational institutions for as little as $199, and subsequently reduced retail prices by $150 this month. That brought the entry-level Surface RT price from $500, to $350.

The company likely decided to go ahead and take the charge early and book it into its fiscal fourth quarter, as it was planning to discount the device.

There were reports last year that Microsoft was hoping to sell 3 million to 5 million units in the fourth quarter alone, ordering up ingredients from component suppliers. Microsoft doesn't disclose unit sales, but IDC pegged the software giant's Surface channel shipments in the fourth quarter at just 900,000.

Regarding Microsoft's ambitions to become a devices-and-services company, the "devices" part of that equation isn't going so well.

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Fool contributor Evan Niu, CFA, has no position in any stocks mentioned. The Motley Fool owns shares of Microsoft. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.