You can pull the URL from a WSS site  and plug it into a portal  site and pull up the Manage Request access  screen. URL: /_layouts/1033/setrqacc.aspx?type=web

I have never done this though (turned on access requests  for a portal) so I would suggest testing it first on a test site and making sure no errors occur and that everything works properly (emails are sent, access can be granted, etc.) I would also check to see where it grants your users access, at the portal level or at the area  level.

With that said, where are your users hitting that access denied  screen? Is it on areas  they don’t have rights to? If that is the case, why not open up the site so you don’t hit this issue? Or are they getting this when they try to do an administrative function they don’t have rights to do like delete an item or change a setting? If so the access denied message is there for a reason.

This method of clubing the url donot work.

Users are hitting subareas  (nt talking abt lists access) where thr site  group dont hv the access. In a broader way , areas  and subareas are like individual sites  and we can provide access  to them the way we do in WSS. But the conflict here is to enable  access request.

WSS site option is ok bt need to try if can be done at portal  site areas and subareas.