SharePoint Search can do so much more than just search your SharePoint sites and one of the features with in SharePoint 2007 and 2010 is the ability to search a file share.
Here is how to configure SharePoint to crawl a file server.
In my environment I have 2 servers. A domain controller that is a file server and also a single SharePoint 2010 server farm.
Configure SharePoint Search
Log into your Central Admin and go to your Search Administration page.
Down the left hand navigation select Content Sources
Select New Content Source
Give a name to the content source and select File Shares as a Content Source Type.
Add the UNC path for the shared documents.
If you want just that folder to be searched select ‘Only crawl the folder of each start address’.
Select up any crawl schedules you want.
Select OK to save this new Content Source
Configure File and Folder Permissions
The SharePoint Search Crawler will run under a user and this user requires permission to the shared folder. To ensure you know which user is crawling you can do this on your file server by opening the File Services Snap In and selecting Manage Session from the Action panel.
You will see which user is connecting to that share.
Add the user to have Read Only permission to that share and folder.