In the Save As dialogue box, you'll want to choose a different format, one that the PC will recognise. The default AppleWorks format won't be recognised by the average PC so I recommend either one of the Office formats or something universal like Text (depending on the original file type of course). 🙁
If applicable, to preserve as much of the formatting as possible, use the "RTF" format. I can/will be recognized by virtually all peecee text apps, like word, notepad ect, at least back to Win98 anyways 😀