Insider trading regulations are designed so that shareholders are treated fairly (relative to each other) as far as access to information is concerned. As long as the decision to exit the hardware market was kept confidential, no problem. If insiders (or people with access to insiders) traded HP stock with advance knowledge of the plan, that's a different story.
With enough degrees of deniability, it's possible that someone traded HP stock based on 3rd or 4th hand information, at which point they acted on speculation that 3rd or 4th hand information was accurate. Very little can be done about that, and it happens more often than you think.
As a Slashdotter, you may be thinking, "Who cares about HP? How can I profit from insider shenanigans without being an insider and risking the wrath of the SEC?"
1. Monitor the options trading activity for a limited number of stock symbols where you suspect insider trading.
2. Build a database that is continuously updated with both option and stock pricing and volume.
3. Watch for a condition in which options activity and volume moves out of sync with the underlying stock. This doesn't prove insider trading, but if insiders are going to cheat, this is the easiest way for them to make a quick buck.
4. Use the options activity as a leading indicator on the stock.
5. Profit!!!!
I am not a financial advisor. This is not financial advice. Your actual mileage may vary.