Restore a content database to a site collection
1st, open share point products->management shell, run:
stsadm -o restore -url http://server -filename c:/wss_content.bak
2nd, if you get the following error:
"Your backup is from a different version of Windows SharePoint Services and cannot be restored to a server running the current version. The backup file should berestored to a server with version '1162887508.196608.17694860.0' or later."
use below:
stsadm -o addcontentdb -url http://server/ -databasename WSS_Content
otherwise run the 3rd step.
3rd,then Go to
Manage Content Databases remove the current site database, and add the wss_content database, iisreset.