Q: My two different DVD players will each play JPEG pictures from processing at the drugstore, but when I copy JPEG files from my hard drive...

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Q: My two different DVD players will each play JPEG pictures from processing at the drugstore, but when I copy JPEG files from my hard drive to a CD or DVD on the computer, neither player will accept the disks. (I seem to remember that this was not a problem when I was on Windows XP.) I know there is a limit on number of files, but I’ve also tried it with only a few. Any suggestions?

Dick Wilson, Everett

A: First a little background on CD and DVD burners. There are two ways of creating readable disks — physically etching the disk, as with old-fashioned vinyl records, or using light to create patterns in dyes on the disk. Commercial disks are etched while “burned” disks employ the dye method. In either case, the disk is read by a read laser detecting the differences in the surface of the disk.

Etching disks is a more costly process, but it is also more reliable. You’ll virtually never find a commercial disk that can’t be read by a player unless it is physically — and deeply — scratched. Burned disks, however, are more sensitive. Some lasers used to read work better with the dyes in some brands of disks than with others.

Also, bear in mind that CD and DVD burners use different lasers for writing than for reading disks. Fact is, it takes a more powerful laser to act upon the dyes in burnable CDs than to simply read burned or etched CDs. If the write laser’s alignment is a bit off relative to the read laser you won’t be able to read the disk.

So first try a different brand of disk to burn. If that’s doesn’t solve your problem, my guess is that the write laser in your CD burner is out of alignment. And, as with much of today’s electronic equipment, you’re going to find it less expensive to replace the drive than to get it fixed.

Q: I travel a lot and always stay at hotels/motels that have wireless service. I have good anti-virus and spyware protection, but I am always concerned about my Internet activity being intercepted by some unscrupulous entity looking for ways to collect personal information. Some of the wireless provided is secure (requiring passwords) and some are not secure (no password required).

So first of all; can my Internet activity be intercepted?

Second, if I use browser favorites, Google bookmarks with Identity Safe logins (Norton 360), thereby not typing most URLs and login information, can this information still be intercepted?

What should I not do when using public wireless service, secure or nonsecure?

Mike Haucke

A: Yes, your wireless activity can be intercepted — all of it.

There are, however, various steps that you can take that provide varying levels of security.

Yes, passwords provide some protection against unauthorized users employing your wireless connection. Passwords, however, are relatively easy to guess or crack. So if you want to prevent unauthorized access, require clients connecting to your access point to have an appropriate security key.

These measures, of course, are rarely employed on public access points since they would require users to manually configure their computers. What’s more, these measures don’t prevent hackers from intercepting your wireless traffic.

The only real security against interceptors is to have transmissions encrypted. Hackers might still intercept the stream of data, but without the encryption code they won’t be able to make any sense of it. Of course, encrypted transmissions work only when the Web site with which you are communicating supports the encryption.

To play it safe, you only want to transmit sensitive information — such as banking information — over encrypted links. If you aren’t informed by your bank that the link is encrypted, you should assume that it isn’t encrypted.

Also, remember that it’s not just transmissions you need to worry about. If you are connected to the Internet, you are vulnerable to hackers even if you’re not transmitting data. That’s why it’s very important that you use a firewall. And just as with other security measures, there are many levels of possible security with firewalls. Generally, the easiest-to-use firewalls are the least secure. Highly secure firewalls require user configuration and customization.

None of these measures individually, or even together, provide absolute security. A knowledgeable hacker can still get into just about any system. But the more measures you employ, the smarter the hacker has to be and the harder they have to work.

Questions for Patrick Marshall may be sent by e-mail to pmarshall@seattletimes.com or pgmarshall@pgmarshall.net, or by mail at Q&A/Technology, The Seattle Times, P.O. Box 70, Seattle, WA 98111. More columns at www.seattletimes.com/columnists.