If you're selling, giving away, or contributing your laptop, the afore mentioned action plan makes a lot of sense. Backup your needed data and then wipe the hard drive by running rescue and recovery, or by mounting it inside another system and using Eraser to "zero out" the drive, and then run rescue and recovery.
Password Exporter, free for Firefox, or IE Password Revealer ($6.99 for Internet Explorer) will help you find your saved passwords for websites, and an external hard drive that you can also use to backup your next PC will make preserving your important data easy.
If the PC is to be destroyed or disassembled, and you're lucky enough to have a floppy drive, starting Eraser from a floppy will certainly erase the drive in unrecoverable fashion.
If you'll be doing this often, or if you find yourself frequently troubleshooting other computers, investing in a heavy-weight tool like Active@ Boot Disk would be a good move. Having Active@ Boot Disk would also make preparing a PC for new ownership quicker and easier.
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