Yes it is possible to crawl content outside SharePoint Portal Server 2003.

Go to 'Site Settings' from your portal home page
Scroll down and click 'Configure Search and Indexing' under 'Search Settings and Indexed Content'.
Scroll down and under 'Other Content Sources' click 'Add content source'
Choose 'File Share' from the radio buttons and click 'Next'
In the address box, enter the UNC path to the folder that you wish to index. *** Remember, your users will need to be able to access the indexed content when it is returned from a search, the address must be a network path accessible from client computers, i.e. your local machine path "c:\xyz\Tech_Ref" will not do - you must share this folder or relocate its contents to an existing network share.
Choose the scope of the search (this folder only or folder and sub-folders)
Choose a Source Group and click 'Finish'
Choose and update (crawl) schedule, select to start a full crawl and then click 'OK'

Thanks for ur valuable help. Now i m able to crawl
outside documents in portal search.