Default Thunderbird XP theme initialy writen for Windows 7 by Michal Stanke. Works also with the Lightning calendar add-on! Initialy updated for TB 45. Now updated for TB 52.1, tested with Vista, Win7 and Win 8.1 by Alain Desgeorge. alain.desgeorge @ gmail.com
Use default theme from Windows XP in newer versions (Vista, W7 and now 8.1). Combining with other add-ons (to suppress Aero/Glass effects) may cause problems. Not intended for Windows XP... not personnaly tested with Win 10
Cannot be updated to work with Thunderbird 60 and later .. Sorry !!
Previous releases you can find on AMO.