I'm confused!
When you send someone a Word document, it doesn't disappear from your computer. The original, unamended, document should still be there. The only exception I can think of is if you sent a document directly from within Word (rather than opening your e-mail client and appending it as an attachment) and then failed to save the original document.
I suspect that, once again, you're trying to send the document from within Word and that your PC is attaching the file which was sent back to you, rather than what you want to send. Try this:
Open the document in Word. Amend it to how you want it to look. Go to File > Save As. Save the file, in a convenient location, with a completely new filename. Close Word. Open Outlook Express (or whatever other e-mail client you use). Click 'New Mail'. Go to Insert > File attachment. Navigate to the location of your newly-saved file and double-click on it. Fill in the address details in the e-mail, together with any message, and send it.
If you follow those instructions, I can see no way in which Outlook Express could send the wrong version of the document. Actually, you should be able to achieve the same result directly from within Word, as long as you use 'Save As', to rename the file, before sending it. (My method simply adopts a 'belt and braces' approach to the problem).
Chris