Set up a guest computer account for visiting family

• Sign in with Facebook, Twitter on other sites
• Back up your computer before upgrading to Windows 8Gas apps can help you save on car fuel

Let guests use your PC or Mac

Q. My family is here for the holidays. I want to let them use my computer, but I don't want them messing with my files and settings. How can I stop this?

A. The Guest account will give house guests limited access to your computer. They can check email or browse, but won't be able to download things or mess with your files. For Windows 7 and Vista, go to the Control Panel>>User Accounts. Choose "Manage Another Account" and select the default Guest account to turn it on. In XP, the Guest Account option will appear when you click User Accounts. For Macs, Click the Apple logo at the top of the screen and select "System Preferences." Click Accounts and then the lock at the bottom of the Window. Select Guest Account from the menu and check the box labeled "Allow guests to log into this computer." For more security features, use parental controls.

Log in with social sites

Q. One of my favorite news sites lets people log in with Facebook instead of creating a new account. Is this a better option?

A. Logging in with social sites like Facebook, Google or Twitter is safer than creating a new profile using weak login information. Many people use the same profile names and passwords on multiple sites for the sake of convenience. However, this means all a hacker has to do is crack your info on that seemingly harmless site to break into your bank account, email and more. So, signing with Facebook is safer — assuming you use a strong password. However, Facebook could track how you surf when you log in to sites using your account. My recommendation is to create new usernames and passwords for every site. If you need help remembering passwords, try a free password manager like KeePass.

Windows 8: Upgrade or clean install

Q. I'm thinking about upgrading to Windows 8. Is it easier to do an in-place upgrade or a clean install of the new operating system?

A. An in-place upgrade keeps most of your settings and programs intact so they'll behave the same way when the upgrade is finished. This process is measured in hours, and with more things to convert, there's more of a chance for failure. A clean install is faster and less likely to have hiccups, but you have to reinstall your programs once the process is finished. A service like Ninite can make quick work of that task, though. Whichever method you choose, make sure you back up before you start in case something goes wrong!

Alternatives to Apple Care

Q. I just bought a new iPhone 5. The sales clerk tried to talk me into Apple Care, but I said no. Now I'm second-guessing myself. Are there any cheaper warranty plans?

A. Keep in mind that your iPhone 5, if bought from Apple, has a one-year warranty for free. Some credit card companies will add an extra year to that if you buy with their card, so you might be covered through your two-year contract. SquareTrade offers a $99 warranty that comes with a cheaper deductible than AppleCare to replace your gadget. Neither of these cover theft and loss, but AT&T and Verizon offer monthly insurance plans that cover that. If all of these sound out of your price range, use the free FindMyiPhone app in case of theft and buy a heavy-duty case to guard against spills and falls.

Save money on gas

Q. My older car is guzzling gas and it's costing me almost $300 a month! Are there any smartphone apps that can help me ease my pain at the pump?

A. I know a couple. Gas Buddy will search your location for the cheapest gas prices available nearby. Gas Price Forecast can tell if prices will be cheaper tomorrow, so you'll know if it's better to top off the tank now or later. Navigation apps like Waze and Where will always keep you on track so you never waste extra gas because you're lost or looking for something. Although these apps can help you find cheaper gas, losing gas mileage could be a sign of an underlying maintenance problem. Car Trouble will help you diagnose those to save you on gas and on maintenance in the long term.

Kim Komando hosts the nation's largest talk radio show about consumer electronics, computers and the Internet. To get the podcast, watch the show or find the station nearest you, visit www.komando.com. E-mail her at techcomments@usatoday.com.