Because of variables such as "we don't know what you'll be doing in the future" all time remaining numbers are GUESSES. And some laptops when you update or install Windows fresh may not offer such a feature.
Did you ASK HP? Sometimes they hide drivers on FTP sites so asking in forums or web sites never works. Here's an example -> http://forums.cnet.com/5208-7587_102-0.html?threadID=271360#2699006
NOTICE THE FTP LINKS! This is why you need to hit hp.com and click on the chat link and ask them.
I've a Compaq Presario CQ 42 laptop with Windows 7 Pro.I find that my laptop unable to tell how much time left for the battery life.I already installed all the driver that I can find in the official website.I find that my friend's laptop are able to estimate the time left for the battery,while my laptop can't show.