Since I've just spent quite a while trying to fix the problem I just wanted to put this out there so other people can avoid having to deal with it.
To start off with the easy solution:
If you want to make a backup of the game with the steam backup function do NOT use the default file name suggested by steam! Just shorten it to Tetrobot or something without "." at the end!
Apparently windows is unable to deal with special characters in the file names and if you go with the steam suggestion of naming the backup "Tetrobot and Co." you will end up with a folder with that name in your backup folder but it will appear to be empty and you won't be able to move it, rename it or delete it.
If you already got stuck with such a file, here's the solution:
- You will have to open the windows command prompt first. - Go to the disk the backup folder is on by typing the letter of the disc followed by : (for example "c:" if the folder is on disc C) (don't type the ") - Go to the backup folder by typing "cd <path of the folder> " (for example "cd C:\Program Files (x86)\Steam\Backups" ) - Type "dir /x" to bring up a directory of all files in the folder and to show their MS-DOS file name - One line in the list should be the Tetrobot file and the dos name should read something like TETROB~1 and behind that should be the full name of the file. - Type "rename TETROB~1 <name you want to give the file>"
After doing so you should find that the formerly empty and unmovable backup folder of tetrobot is now actually a real file again that can be moved, renamed and deleted like you'd normally expect.