Deleting old torrent files in User/AppData/roaming/bittorrent completely corrupted program

[eb99]

While trying to reduce the size of my C: drive backup, I found that Bittorrent had been keeping all of the .torrent files I had ever used for downloading since I installed the program eight years ago. They were in User/Appdata/Roaming/Bittorrent. I manually deleted all but the last year of those files, 20k files totalling 1.16Gb. That caused Bittorrent to corrupt unrecoverably, the program disappeared and when I tried to delete in Control Panel, it said it was already deleted. When I tried to reinstall, it got to 47% unpacked and crapped out. I don't understand what has happened here, and I don't see why:

a) Bittorrent keeps the .torrent files after a torrent is deleted

b) Bittorrent totally corrupts if you manually delete old and unneeded .torrent files.

[eb99]

I only deleted what seemed to be the .torrent files, not any of the folders.

I eventually figured out that (breaking the first law of system design) the executable file was mixed in with the data files, and it had been deleted. I copied over the most recent installation file I had into that folder, ran it, and got the option "Newer version installed, do you want to go back to Version 7.9.9?" Since I knew the newer version was gone, I chose 'Yes' and an older version was installed. It did run successfully and picked up all the outstanding torrents. However, when I tried to update, it said no newer version was available. I thought that might be because of the update folders for newer versions, and deleted all beyond the 7.9.9 version, but that didn't make a difference.