For a sense of how bad things have been at Hewlett-Packard in recent years, consider this. The stock drop on the day it ate $8.8 billion of an $11.1 billion acquisition wasn't its worst market plunge in history. The 12 percent dive to 10-year lows on Tuesday was just the sixth worst for the Palo Alto tech giant (NYSE:HPQ). The biggest one-day collapse in HP's stock price came about 15 months ago when it sank 20 percent on the day it announced it would buy British software company Autonomy, the…