it depends on your hosting account.
if the subdomain has access to the main domain name files then yes, if not then no.
you can try by finding out if you have access add the following to a page on both the sub domain name and main domain name.
this with give you your physical location on the server
as an example i will use the following as a file structure
/www/domain.com/
/www/sub.domain.com/
using the above as an example you would use the following code to include a file from "domain.com" in "sub.domain.com", this will be in a page on the root of sub.domain.com
<!--#include file="../domain.com/include.asp"--> |
the "../" means go back a folder, so if its in a subfolder on "sub.domain.com" add two, or how ever many you need