Here is an MSDN page which covers Duplicate detection through and through:
http://msdn.microsoft.com/en-us/library/cc150958.aspx
The following with thanks to Donna:
You can set Status to Match. Although this will not completely stop checking against inactive records it will eliminate duplicates showing for multiple records where the status is different.
Only active or inactive records with the other matching criteria you set will display.
http://social.microsoft.com/forums/en-us/crm/thread/AD5B4878-89C5-4BA5-A922-3EDBE4AEF85C
Jeff Loucks | Available Technology | 888-474-2237 | http://msmvps.com/blogs/jeffloucks