Windows 7 is not able to index the contents of network shares or mapped network drives. This has been frustrating me and many others for some time. There is a workaround for this detailed below:
Example - your old windows xp machine has all your data stored on it and windows desktop search 4.0 installed and indexed. You have a Windows 7 PC and you want to search for files on the win xp machine but the inbuilt desktop search cannot index netwoked computers or drives.
Solution - On the windows XP machine Install windows desktop search 4.0 and index all the files and folders you wish to search.
share the folder or drive on the windows XP machine.
In windows desktop search options add a unc path eg \\server\drive
On the windows 7 machine, map the network drive from the windows XP machine to a drive letter.
log onto the mapped drive using the user name and password you would normally use to log onto the windows XP machine.
On the windows 7 machine open the mapped network drive and type the words you want to search for in the search box at the top right of the window. The indexed locations in windows desktop search 4 should quickly appear on the windows 7 machine.
How it works - Windows 7 search is retrieving indexed information directly from windows desktop search 4 on the windows XP machine without having to re-index the mapped drive. This is a much more efficient method of searching than the microsoft recomended method of enabling offline files and basically storing local copies of all your network shared files.