I have done the indexing  already. But there in no
change in the search  results..i.e it does not show the
content from the old WSS site.
Is there any other way of using the SPS search from
the WSS site  itself??

Could you not back up the old wss  site and then import the old wss site  into the new sps  Portal using smigate.exe.

www.microsoft.com/.../details.aspx

This may solve the issue in one go.

I have tried to do this earlier on a different server
i.e installed Sharepoint portal server 2003 in a new
server and import the old site, but I got the error
saying that the database schema is too old.
Now I have installed Sharepoint portal server 2003 on
the existing development Server which has got the WSS
site in it.( The old site  still works the same way
without much effect of SPS in it). I have created new
portal site in the same server and am trying to link
the sites database to this. But I am unable to do it.
But I have linked Portal to search  the old site . But
the Content is not searched. It does display the site
when search for it.
I am still looking for solution to use Portal features
in the old WSS site.