I recently upgraded from a G4 tower to a spanking new G5 Quad, and since my old computer was in tip-top shape I thought I'd save myself some setup time by choosing to "migrate" all the data from the old computer to the new one.
Everything seemed to go well...I fired up the new G5 and was pleased to see it basically looked and felt like my old system, with all my folders and apps where I expected to find them. I noticed, however, that some 'migrated' folders had the tag (from old Mac) added to their names. Very helpful, I thought, that the migration process tagged these folders this way lest I lose track of what was old and what was new on my computer.
The problem this seems to cause, however, is that a few of my Classic apps (I know, I know ... a G5 Quad and I'm still running Classic. I am merely a prisoner of the slow-to-upgrade corporate environment in which I work!) lost track of where they could find extensions, plug-ins, etc. that they needed to function properly. QuarkXPress 4, for example, couldn't find some of its extensions or my auxiliary dictionaries, and had trouble launching (calling up dialogue windows asking me to locate these things, whch frequently froze the launching process). An old version of PowerPoint couldn't find some obscure Microsoft library files.
The fix, simple as it was, was to remove the (from old Mac) tag that had been added to my OS 9 System Folder folder's name. This restored the accuracy of the 'links' that my Classic apps needed to find their extensions, plug-ins, etc. and everything returned to normal.
This issue may have more far-reaching impact than I've run into. It seems changing the Sysem Folder folder's name was not such a good idea after all.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060719072306358