By default, the search service is disabled in WSS 3.0. In order to enable it, goto your SharePoint Central Administration page and under the Operations tab, goto the "Services on the Server" list and click on WSS Search.
- Service Account - You cannot use any built in accounts when specifiying the Service Account, however you can use local accounts. One account you can choose to use is the default Administrator account on your server, "myserver\Administrator".
- Content Access Account - Use an account that has full read access to your SharePoint Content Databases. As a security precaution, try not to use an account that has write permissions on the database. For example: "mydomain\sqlserveruser".
- Search Database - In most cases the default settings will work, change them as required.
- Indexing Schedule - No new files will be searchable until they are indexed, depending on the load you wish to put on the server you can set this to be done as often as you want.
Upon submitting the form, the search service should start and begin indexing the content in your SharePoint site. Now would be a good time to install the Adobe IFilter to allow your search service be able to index PDF files, the earlier you install it the better, since it will only recognize PDF files added after the addon was installed.