Check these links.
http://wiki.sdn.sap.com/wiki/display/ERPFI/Basics+of+Asset+Accounting+-+Asset+Retirement
http://wiki.sdn.sap.com/wiki/display/ERPFI/Asset+Accounting
Also EAM is not the right forum to discuss this topic. Use the below given space for this.
http://scn.sap.com/community/erp/financials/asset-accounting