Wow, here are a whole bunch of thoughts. (As-is, no warranty).
1) Apparently you're getting an error message that the path or filename is too long for Windows to delete the file. I'm guessing the problem is more about communicating to the Windows shell what file you're trying to delete, as opposed to some problem with actually deleting it. MS Command Prompt and Cygwin both provide multiple ways to specify a given file besides the full file name, for example using wild cards, regular expressions, etc. For example, I would try something like "rm A*" in Cygwin or "erase A*" in Command Prompt, where "A*" is a wildcard that expands to only the file you want to delete. Individually, I'd give this maybe a 50% chance of working, but if it doesn't work, maybe something further down this list would
2) Likewise, you might be able to use Command Prompt or Cygwin with wildcards to rename or move the file, so its path and filename are shorter. If you can successfully do that, I'm guessing deleting it would then work.
3) You could also try using Command Prompt or Cygwin to delete the whole directory, making sure that file is the only one in it. For example "rm -r <Directory name>" in Cygwin.
4) In the old days (when I was a kid), MS DOS used to require file names to have maximum 8 characters, upper case, and with no special characters like space or comma. If I'm not mistaken, Command Prompt can still refer to files with this type of name. In general, I think take the first 6 characters of the name, followed by ~ and a numeral. For example, "This is a long filename.txt" can also be referred to by something like THISIS~1.TXT. So I would try to use something like "erase THISIS~1.TXT" in Command Prompt.
5) Maybe a compiled program could overwrite or delete the file, as a way to circumvent the OS shell. For example, you could try opening the file with vi in Cygwin or some other low-level text editor, removing the file's contents, and re-saving. Or you could write your own compiled code to delete this file, but I would make sure to use file handling commands native to the language, like 'open' or 'write', as opposed to any command that invokes the OS shell.
6) Finally, maybe you could just overwrite the file by redirecting the output from some other command, for example "echo 'Null set' > A*" in Cygwin, where "A*" is again a wildcard that expands to just the file you want to overwrite.
