First off, you need to escape your back-slashes. Use C:\\webserver\\osarr.org\\www\\cgi-bin\\data\\indsignups.txt for your file to be opened. In unix it was probably something like /webserver/osarr.org/www/cgi-bin/data/indsignups.txt which works because unix uses forward-slashes...

Second, you gave us way too much information. Now, that's better than not enough, but I think since you knew the problem was with not finding the file to output to, that's the only code you needed to show us.