Try saving this as web.config and place it in the root dir:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<location>
<system.webServer>
<httpRedirect enabled="true" destination="http://www.newsite.com/" httpResponseStatus="Permanent" />
</system.webServer>
</location>
</configuration>
If you cannot manage the site in IIS but can change the files replace them all with
<%
Response.Status = "301 Redirect"
Response.AddHeader "Location", "http://new.com/foo"
%>