You can find the file with all messages in the directory where Offline Explorer is installed. It has .int extension. Choose the file that contains the language you are using. For example, English file is oe_en.int. Open the file in a Text editor, find the desired message and change it for your requrements.
I hope this helps.
Can you please also tell me, what changes you would like to make there? This suggestion might be useful for other users as well. Thank you.