UDF vs ISO: Why won't my CD-RW work in Another PC?

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Infopackets Reader Philip S. writes:

" Dear Dennis,

I use Windows XP and I often write my data to CD-RW (CD rewritable) discs. The problem is that some computers won't read the discs that I've created, whereas others will. I'm pretty sure the problem has to do with the format I'm using when I create the disc, but I'm not sure how to tweak the settings so that the discs are compatible on all computers. I am currently using Windows XP and Explorer to write the discs, using UDF format. Any ideas? "

My response:

You're correct -- the problem is with the UDF disc format and / or the way that you are creating the disc. When it comes to creating a CD or DVD and having the best compatibility possible (whether you're using music CD players, DVD readers, or computers to read the discs), the ISO:9660 or "disc at once" format wins hands down.

UDF vs ISO: A Quick Comparison

The ISO:9660 format has been used since 1988 whereas UDF has been around since 1995 and continues to be revised. In short, UDF has a number of revisions and newer formats may not be compatible with older operating systems.

UDF is extremely convenient because it supports packet writing and because it is built into most modern operating systems. In other words, you can drag and drop files to a CD or DVD whenever you want, and it writes data to the disc "on the fly".

The downside to using UDF is that the disc format may not be compatible on other systems, plus UDF isn't supported on many CD and DVD players (especially older hardware). If a computer can't read a UDF disc, you might be able to get around the issue by downloading and installing third party UDF reading software. At this time I am unaware of freeware UDF readers for Windows with up to date specifications. Anyone reading this article is welcome to chime in with suggestions.

In comparison, the ISO:9660 "disc at once" format, or "DAO" is compatible with virtually any device including CD (music) readers, and DVD (video playback) readers, and all operating systems.

The downside to using ISO:9660 format is that you might need third party software to properly write an ISO (you can use CDBurnerXP -- it's free). Also, you will need to write the entire contents of the disc in one go, which means it requires some planning, is not convenient, and may result in wasted media. Another ISO format supports writing multi-sessions (meaning you can write more than once to the disc) but this format is not as compatible at the disc at once method (especially for CD readers), plus it eats up memory on the disc every time you write a new session.

Further Reading

This answer only scratches the surface of the topic. If you want more reading, please review the ISO:9660 format, UDF format, ISO:13490 (multi-session) format, a comparison of various CD formats, and reasons why UDF doesn't always work (especially with Windows XP). Or you can take my word on the topic, and just write an ISO disc at once.

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About the author: Dennis Faas is the owner and operator of Infopackets.com. With over 30 years of computing experience, Dennis' areas of expertise are a broad range and include PC hardware, Microsoft Windows, Linux, network administration, and virtualization. Dennis holds a Bachelors degree in Computer Science (1999) and has authored 6 books on the topics of MS Windows and PC Security. If you like the advice you received on this page, please up-vote / Like this page and share it with friends. For technical support inquiries, Dennis can be reached via Live chat online this site using the Zopim Chat service (currently located at the bottom left of the screen); optionally, you can contact Dennis through the website contact form.

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