Sooner or later, every laptop owner asks the same question: How long will my battery last? For most people, sadly, the answer is the same: not long enough. But there are plenty of things you can do to squeeze every last minute of power out of your notebook's battery.

Use power management:
Judicious use of your notebook's power-management software can translate into many minutes of extra computing time. If your notebook comes with a power console applet that lets you create customised power profiles, use it to adjust the settings until you get the right mix of functions and battery life. If your laptop doesn't have such a program supplied by the notebook vendor, use Windows' perfectly adequate Power Options utility in Control Panel (it's called Power Management in Windows 98).

Dimmer is a winner:
A big laptop energy sink is its LCD screen. Reducing the screen's brightness conserves battery life. For example, when I work on a red-eye flight, I can squeeze up to 45 additional minutes out my Sony Vaio notebook by toning down the screen brightness. Most notebooks have an easy-to-access keystroke sequence, function (Fn) key, or software utility for adjusting this variable.

If a dim screen is good for battery life, a blank one is better. Windows' Power Options/Power Management utility lets you tell your notebook how long to wait before blanking the screen. In Windows XP and 2000, open Control Panel, select Performance and Maintenance (if you're in Category view), and click or double-click Power Options. In Windows 98, open Control Panel and double-click Power Management. On the Power Schemes tab, choose Portable/Laptop in the 'Power schemes' drop-down menu. In the menu next to 'Turn off monitor', choose the length of time the screen can sit idle before it goes blank. The shorter the interval, the more power you'll save. The shortest option, 'After 1 min', may drive you nuts, however.

The Power Options and Power Management programs have settings for your notebook's other big power glutton - the hard drive - as well. Once again, you'll need to find the setting that works best for you. Remember to reduce the frequency of auto saves in PIMs, word processors, and other software; your hard drive may otherwise lose power-saving sleep.

Go unplugged:
Remove PC Cards and USB or FireWire devices that you don't need. If your PC has a built-in wireless card, turn it off or disable it when not in use.

Make like a bear:
Most PCs have Hibernate and Suspend modes that are easy to activate from the keyboard. Check your notebook's documentation for its setting. Suspend (also called Stand By mode) typically holds your current information in RAM with a minimum of power, so the system comes back to life quickly. Hibernate writes everything to disk and shuts off, so it saves more power than Suspend, although it also makes reactivating your PC take longer. Still, awakening a hibernating system is much faster than cold-booting one that has been turned off.

Lean is green:
To keep your laptop's CPU from doing unnecessary work, shut down any hardware or software you don't need. Check the icons in your system tray (on the bottom right near the clock); there's a good chance you can shut most of these down, though they will likely restart the next time Windows loads. Browse to last June's Windows Tips column, "Make Windows Start and Stop the Way You Want," and scroll down to "Stop Autostart Apps" for instructions on how to disable programs that start automatically with Windows.

To track the effect that different programs have on the CPU in Windows 2000 and XP, press Ctrl-Alt-Delete to open the Task Manager. Select the Performance tab to see a handy graph of CPU usage. In Windows 98 and Me, this information resides in System Monitor: Click Start, Programs, Accessories, System Tools, System Monitor to open it.

Disable devices you don't need that may draw a small amount of power when on but not in use. For instance, if you're on a long flight, you probably won't use your modem, your network card, your parallel and serial ports, and possibly your DVD or CD-ROM drive. You can easily disable all of these in Device Manager. To open Device Manager in Windows 98 and Me, right-click My Computer and choose Properties, Device Manager. In Windows 2000 and XP, right-click My Computer and select Properties, Hardware, Device Manager. To disable a device, right-click its listing under the appropriate category and choose Disable.

If you'll be disabling devices regularly, save time by creating a Windows hardware profile.

Improve your memory:
Adding more memory to your laptop saves power by reducing Windows' reliance on the virtual memory swap file on your hard disk.

Rub it down:
Clean your battery's metal contacts every couple of months with a cloth moistened with rubbing alcohol.

Carry a spare:
Purchase an extra battery pack, if you can afford it. Expect to pay $85 to $235, but shop around for bargains. Battery-vendor Web sites and EBay are good places to start your search.

If you can splurge a bit, you'll get up to three times your current battery life with the MaxPower 60 Powerpack battery from Lind Electronics. The 3-pound MaxPower 60 is only 0.5 inches thick and about the same width and length as a standard laptop.

Charge frequently:
Carry a battery charger/AC adapter with you on the road, and plug it in whenever you get the opportunity. If the power adapter that came with your notebook is too bulky, check out universal power adapters offered by the likes of Belkin and Targus. The adapters are thin and light, and the Targus model doubles as a charger for your cell phone.

For road warriors and frequent fliers, Targus and Belkin offer power adapters that plug into 12-volt outlets, such as car lighters.

Drain it:
If you have an old laptop that uses a nickel-metal hydride battery, completely drain and recharge the battery once a month to maximise its capacity to hold a charge. Most new laptops use standard lithium ion batteries that need not be drained to maximise their chargeability.

If you're in the market for a laptop, you'll get the best battery life from systems that are based on Intel's Centrino platform. As with any new technology, however, check reviews before you buy. Graphics chips, peripheral interconnects, and many other factors can influence notebook battery life. Real-world results may not mirror the vendor's performance claims.