You can import a wide variety of file formats into RoboHelp (e.g. XML, HTML, PDF). You'll have to tell us a little more about what you have available. For example do you have access to the source files or just the output? Also what type of output is it. There is a way to migrate your content though so don't dispair.
Shoot a message off to Willam van Weelden (wvanweelden.eu) - it appears that he ran across some Doc-To-Help legacy projects that needed converting last April (2012) - here's the thread - http://forums.adobe.com/message/4307205
I have access to the source files (Word docs) as well as the HTML output. I am thinking since I have the source files (Word docs) I can just import them into RoboHelp. Do you have another option? Thanks.