AxCrypt 2 can open all AxCrypt 1 files (if you know the password).
AxCrypt 1 cannot open AxCrypt 2 files.
AxCrypt 2 will by default automatically convert all opened files to AxCrypt 2. This can be turned off.
You can’t have both installed at the same time, but you can have AxCrypt 2 installed, and keep AxDecrypt, the v1 decrypt-only stand-alone program on the computer. You can also have AxCrypt 1 installed, and use the fully features AxCrypt 2 in standalone mode. See the downloads page.