Here's the fastest way to get all the missing fxs files:
Go to http://www.microsoft.com/downloads/details.aspx?familyid=A8F72FDD-6D82-4C2B-8078-114460826A40&displaylang=en
Download the file, but don't run it, just save it ( Because it's intended only for Server2003 installations).
Open it with Winzip or other Zip reader, 7-Zip Freeware .
After you Saved that File right Click on it & Open it with 7-Zip extract the files to a convenient permanent folder, and point the FAX installation there to access them