Make Windows 7 Search files from the mapped or network drives

1. Click the Start button and type in Windows searches.

2. Click on Change how Windows searches.

3. Now click on the Advanced button and select the File types tab.

4. Scroll down and locate your file type and make sure that the radio button Index Properties and File  Contents is selected for the file type you are trying to find.

Once this is done the windows search will do an indexing of all the files on your computer or mapped folder. 

http://support.microsoft.com/kb/2268596