Any keylogger can also read your plain text file. And if you encrypt the file the keylogger can read you typing your decrypt password.
Moral: Use a good anti-spyware program like your life savings depended on it.
Me, I do all my banking from my Linux computer. My Windows machine is only for things that REQUIRE Windows. For everything else I uses the system that (for whatever reasons, different argument) doesn't attract spyware.
"And if you encrypt the file the keylogger can read you typing your decrypt password.
Good encryption programs do not go through the standard keyboard driver, but use their own. This blocks software, but not hardware, keyboard loggers.