Deleting backup files

[Theresa de Valence]

Could someone please give me a command for deleting backup files in 
Windows (Windows 7)?

This is for the end of the project when I am no longer opening all the 
working files.

I'd like the command to work in the current directory and all 
subdirectories.

I vaguely remember how to do this in DOS, but I don't know how to 
navigate directories which are longer than 8 chars!

Many thanks,
Theresa