For asp, you can use the Session.Timeout property:
<%
Session.Timeout = 45
%>
to make this application wide, you may want to create a global.asa file at the root of your site with the following:
<script language="vbscript" runat="server">
sub Session_OnStart
Session.Timeout = 45
end sub
</script>
See the following for more on the glbal.asa file:
asp_globalasa.asp
and the following for more on the session.timeout property:
prop_timeout.asp