If you think your computer is being watched: Someone may have sneaked surveillance software onto your computer. Reformat your hard drive, then reinstall your operating system, programs and documents. Install a spy-software detector such as Spybot (free; spybot.info), then change all passwords and PINs. Extra-paranoid? Plug in a device such as APC's Biometric Password Manager ($50; apc.com), which lets only someone with your fingerprint (that is, you) log on. If someone appears to be accessing your computer remotely, make sure your Wi-Fi network's security is turned on, then install a firewall and antivirus software to ensure that only trusted files move in and out. One to try: ZoneAlarm Security Suite ($60; zonelabs.com).