On the XP virtual machine, where you have both OE and TB, open TB, then Help/Troubleshooting Information, click Show Folder to open the profile folder in Explorer. Go 'up' 3 levels in the directory tree so that you can see the Thunderbird folder, a subfolder of Application Data, and copy this folder to a location that is accessible from the Mac side.

C:\Documents and Settings\<Windows user name>\Application Data\Thunderbird\Profiles\<Profile name> is the profile path in XP.

Now, open TB in the Mac and from Help/Troubleshooting Information, click Show Folder to open the profile folder in Finder. The location is given here.

Exit TB, and once again go 'up' in the directory tree to display the Thunderbird folder, and delete it. Finally, copy the Thunderbird folder that was saved in the virt. machine into the same location where you just deleted it, restart TB, and you should see all the data that was in the XP TB.

Thank you for the suggestions. Actually, that is in essence what I had tried unsuccessfully. I pursued the issue some more and have identified a solution. The basic problem for me appears to be that the Library on MacOS10.8 and others is hidden and cannot be modified. The steps I took are as follows: 1. As indicated in the original question, I loaded TB24.4.0 on my WinXP. I was able to load all my dbx folders from Outlook Express into this copy of TB. The folder structure was present as desired. As noted by sfhowes, the TB folder is accessible. I copied TBnameX.default from Documents&Settings/Owner/ApplicationData/Thunderbird>Profiles/TBnameX.default to the Mac desktop. 2. Load Thunderbird24.4.0 into the Mac, if not done earlier. (perhaps: Open TB. Close TB.) 3. While in the Mac desktop, hold down <Option> key while clicking on <Go> in the top bar menu. This makes the Library unhidden. Clicking on Library in the Go list, opens Library in a Finder window, and Thunderbird is now unhidden in the directory listing, and is accessible. 4. Navigate Thunderbird/Profiles/TBnameM.default . Delete TBnameM.default. 5. Copy or move TBnameX.default to the spot in the Profiles from which you deleted TBnameM.default. Opening TB, however, may show the prior profile defined by TBnameM.default. Opening the profile.ini and replacing TBnameM.default with TBnameX.default was not sufficient to give the desired profile. 6. Shutdown and reboot the computer. Open TB. The desired profile is present, & TB seems fully operational. I will need to manage somewhat differently from in OutlookExpress, but the important folders are now available to me. Thanks.

I'm glad you got it to work, but just to clarify, transferring the entire Thunderbird folder, rather than just the profile subfolder, is suggested because it makes it unnecessary to edit profiles.ini.

Switching from one OS to another means certain preferences in the profile will not transfer properly, such as attachment opening applications, but the remedy for that is to delete mimeTypes.rdf from the profile folder and have TB create a new, empty version. The correct preferences will be defined the first time you open attachments.