Since you have the disk version (No Steam), you do not need to rename your Third_Age_3 folder.
Delete that same Third_Age_3 folder which you had just installed, and doesn`t work.
Now, before installing TATW, what you need to do is take ownership of your main Medieval II TW folder. Since you have Win 8, use these instructions: Follow "
How to take Ownership of files & folders"
Thanks for your answers, i got the main game+ MOS to work, it is working and i am having alot of fun with it. The only problem i have encountered so far was an unexpected crash when i was looking over the map. Any fixes for this or is this inevitable?
After taking ownership of your main Medieval II TW folder, install TATW files again. After installing TATW files, be sure to
disable/turn off Automatic daylight saving setting, which can crash your battles.
Good luck!