I got one friend, his laptop is newer than mine. However, the battery is already working bad. The battery will lost the power quickly. But my laptop’s battery still can work about 1 hour plus.

And I just read about lithium-ion battery (which is used in laptop, PDA, and handphone). The following is the quotation from http://electronics.howstuffworks.com/lithium-ion-battery.htm/printable.

Lithium ion chemistry prefers partial discharge to deep discharge, so it’s best to avoid taking the battery all the way down to zero. Since lithium-ion chemistry does not have a “memory”, you do not harm the battery pack with a partial discharge. If the voltage of a lithium-ion cell drops below a certain level, it’s ruined.

Recently, I read a news about that there is PDF flaw. I am not sure how is it happened. But you can read a news about this PDF and trojan problem:
http://www.eweek.com/article2/0,1759,2205400,00.asp?kc=EWRSS03119TX1K0000594

Beware of the PDF file when you receive a spam mail. The PDF file will disable the Windows Firewall, and download the trojan file.

I also read an article talk about that some people like to run the Windows with reduced rights (non-administrator rights). Because this can disallow the modification of you Windows system, such as installing unwanted programs.
http://www.techsupportalert.com/how_to_easily_run_programs_with_reduced_rights.htm