Ian,
Just a hint: in Control Panel -> Folder Options -> 'View'-tab, you may want to switch
off /
disable the option "Hide extensions for known filetypes" (this is what it's called in WinXP/Vista. Don't know exactly in Win7 though)
This option is in fact a bitch, especially when working with the files themselves like you have experienced just now (and trust me: you will find yourself doing this more often then you may want to). There is FS9.ini, FS9.exe, FS9.dll: when file-extensions are not displayed, how are you going to tell the difference easily between these files!?!?
M$$ and their continous ever lasting efforts to 'dumb down' the end-users with such totally useless features which only lead to problems...

Cheers,
Stef