If you have access to a Mac with iWorks, supposedly it will open old ClarisWorks files. Then you can save it into something that can be read by a Windows program.
Or for $30, you can order a Windows-based program to convert them:
http://www.macdisk.com/mactxten.php3I've seen mention of AbiWord being used to open them and save them as a different format on the OpenOffice.org forums. AbiWord's website lists a converter for the files, but the converter is still in development and may not open the files properly:
http://www.abisource.com/According to Microsoft, up to the 98 editions, no MS Office products would open ClarisWorks files. I'm not sure about newer ones as they don't mention anything beyond that (I assume this article is old).