Shares of Hewlett-Packard (NYSE: HPQ) were down more than 20% yesterday, 10 months after I told investors to short the stock. Thursday night, the world's top computer maker reduced guidance and announced plans to exit the PC and mobile-device business.

"Mark Hurd is the lucky one. If you're buying shares of [HP] right now, you're unlikely to escape losses owning this scream-worthy stock," I wrote in profiling the stock for our annual Halloween special. Shares of HP have underperformed the market by more than 40% since.

(Sigh.)

I'd love to have been wrong about this. Good people are going to get hurt. Talented men and women will lose jobs. Investors will lose savings as HP loses face. Almost no one gains from this. Except, of course, for Apple (Nasdaq: AAPL).

The remains of HP's days as a PC company
More on all that in a minute. First, let's review the numbers. Revenue rose 1% to $31.2 billion in HP's fiscal third quarter, about in line with estimates, while non-GAAP earnings rose 2% to $1.10 a share. Analysts had been expecting $1.09 a share of adjusted earnings. That's the good news. The bad? HP reduced guidance for both the fourth quarter and full year.

In Q4, management  expects $1.12 to $1.16 in adjusted earnings on $32.1 to $32.5 billion in revenue. For all of 2011, HP expects $4.82 to $4.86 in adjusted profit on $127.2 billion to $127.6 billion in revenue.

Neither estimate came close to meeting Wall Street's projections. Analysts had been calling for $1.31 a share in Q4 profit on $34.04 billion in revenue and $5.01 a share in full-year earnings on $129.15 billion in revenue, according to data compiled by Yahoo! Finance.

Sagging sales for the PC and devices group -- the division HP calls "Personal Systems" -- was at least partially to blame. Revenue from that unit fell 3%. Consumer Client revenue declined 17%, most likely because of the rise of the iPad and iPhone. Or at least that's how CEO Leo Apotheker made it sound in his comments to analysts during the earnings call.

"Secular trends impacting our PSG business as consumers are changing the use of the PC. The tablet effect is real, and sales of the TouchPad are not meeting our expectations," he said. Right. Secular trends such as Apple's sales of 5 million more iPhones than anyone expected last quarter.

Apotheker would go on to explain how a sale of Personal Systems assets -- including the WebOS platform acquired from Palm and the entire PC business -- would help to sharpen HP's focus on the cloud and technologies for accessing services from "any type of device."

HP's post-PC era
Why not just rename HP after Apotheker's former employer, SAP (NYSE: SAP)? We could call it HP-SAP. Or SAP Enterprise. Either way, in exiting the consumer business, Apotheker is returning to his roots -- and aiming for Oracle (Nasdaq: ORCL) and IBM (NYSE: IBM) in the process.

Again, consider Apotheker's own comments. Enabling access to any type of device means selling servers, storage, database technology, management software, and (as I'm sure Apotheker would hope) more than a dollop of professional services. HP offers all this and more today, and it plans to further beef up its back-office offerings with a $10.25 billion bid for Autonomy, a U.K.-based provider of software for optimizing data infrastructures.

Less brains!
When HP bid for Palm last April, I called it one of the worst deals I'd ever seen. In October, I predicted that HP's inability to glean value from the acquisition would take a toll on shareholders. The company had become a corporate zombie, I contended, eating brains for no other reason than to eat brains. Today we're seeing the effects of its indigestion.

To be fair, Apotheker is probably right to solicit bids for WebOS and Palm. A recent rush to acquire patents could value Palm's own intellectual property at a multiple to the $1.2 billion HP paid. Consider Google (Nasdaq: GOOG), which has committed what amounts to an $8 billion premium (over book value) for access to Motorola Mobility's patents.

Yet there's a huge difference between selling off underperforming assets and cultivating high-performing assets in the sort of competitive environment in which HP operates. The former is a guarantee; the latter anything but. Or as Apotheker put it during the company's earnings call:

The transformation we are undertaking will take several quarters to fully resolve. I don't take this action lightly. I know our investors don't like being in this position, and neither do I. I feel their pain. But as CEO, I believe in transparency about what we are facing and be clear on the decisive things we are doing now about it.

There you have it. Zombie HP may be dead, but the nightmare is just beginning. Do you agree? Disagree? Weigh in using the comments box below. And if you're in the mood for more stock ideas, try this free video. You'll walk away with a better understanding of the cloud-computing revolution that HP is hoping to profit from, as well as a winning pick from our Motley Fool Rule Breakers scorecard. Start watching now -- it's 100% free!