First install Aid4Mail on your old computer and activate your license.
Next, transfer the resulting ZIP file to your new computer and install Aid4Mail on it; then re-activate your license.
You only need to use Aid4Mail on your old computer if you have Qualcomm Eudora mail.
In this case, first install Aid4Mail on your old computer and activate your license.
On your old computer, use Aid4Mail to convert your Eudora mail to the Generic Mailbox format.
Next, transfer the resulting mbox folders and files to your new computer and install Aid4Mail on it; then re-activate your license.
Finally, use Aid4Mail to export your mbox files to your new mail program.
For other formats, simply transfer your source mail folders to your new computer and then use Aid4Mail on your new computer to export them to your new mail program.