There is not one specific manual for this computer. That depends which mainboard is used. If you post your serialnumber (it's on the back of the PC), than I might be able to check.
Manuals can be found on this site: http://manuals.fujitsu-siemens.com/homepc.html. If you know your mainboard you can find it there. If you still have the Drivers & Utilities CDROM than you can find most manuals there even more easily.