Files related to removed email accounts are not deleted.

Thunderbird (currently 24.6.0, Windows) current Account Settings window shows Local folders and RSS folders for rss feeds. I used to have 2 email accounts, but a long time ago I stopped using Thunderbird for them. At that time I removed them using the "Remove account" button. They were (and are) no longer displayed. The other day, I went to transfer Thunderbird settings using MozBackup to another system. On that system I could see the two email accounts (including mail messages). Then, I checked in the Thunderbird Profile folder in Application Data. The accounts were still there. So my question is - How can I completely delete the old email accounts. I read elsewhere that the primary email account cannot be deleted. But can the account sub-folders in the Profile folder be deleted without causing other problems?