As we approach the launch of Mac OS X Lion there are a few checks to perform before downloading Lion.  Snow Leopard has a helper application, called Rosetta, that runs in the background to make older applications run like they were written for new Macs.  Rosetta was designed to help smooth the transition from PowerPC processors (used in all Macs before 2006) and Intel processors in the current Macs. Think of it as being the difference between English and Chinese, a translator is needed.  Rosetta is was that translator.  Rosetta is not included in Lion making any application written with PowerPC code incompatible.

Before you upgrade to Lion, you need to find out which applications rely on Rosetta.  To do this go to your Applications folder.  Single click on the application you want to check.  Go To File Menu > Get Info (or keyboard shortcut Command + I).  Look at the line labeled Kind. If you see PowerPC after Kind: Application (see photo), it will not work in Lion.  Repeat this process for any programs you will need to use with Lion.

You can also see a list of all applications by going to the Apple Menu > About this Mac.  Then click on More Info.  Select Applications in the left column. Look at the Kind column and any application that’s kind is listed as PowerPC will not run in Lion.

If you found some applications listed as PowerPC you will need to make a decision.  Upgrade those applications or hold off on your upgrade to Lion.  If you choose to continue with your upgrade to Lion check with the developer of your software to download a newer version of the application or replace it with an different application.

Here are a few of the most common applications that use Rosetta:

Quicken for Mac 2007 and older

Best Replacement: iBank. iBank will import your quicken data and closely matches the feature set of Quicken 2007.  Quicken Essentials 2010 does not have all the same features at Quicken 2007 or iBank.

AppleWorks, all versions

Best replacement: iWork. iWork is made by Apple and will open AppleWorks word processing and spreadsheet files. Pages for word processing and Numbers for spreadsheets.  However it will not open AppleWorks database files.  If you have an AppleWorks database you will need to manually move it to a new database application like Bento.

Microsoft Office for Mac 2004 and older

Best Replacement: Office for Mac 2011. Office 2011 will open all of your Office 2004 files so you can keep working without a hitch.  If you want to save some money iWork will also open your Word, Excel and PowerPoint 2004 files.

Other applications with newer versions available.

All of these applications have been updated to the latest code so the will be compatible with Lion.  Adobe CS1 and older, FileMaker 8 and older.

As with any new Operating System release you should always check with the maker of any application before installing a major OS upgrade.  While most programs will work fine or have an update available it is best to check before upgrading.