Uninstall all video drivers via the control panel and turn off your computer, add the graphics card then install the drivers for the HD4650 (from the AMD site).
Also, see if there's anything in the BIOS about it.
Your motherboard has a very poor manual - it provides rudimentay instructions for changing the CPU - which hardly anyone does with such systems - but not a word about what if anything is required when installing a graphics card or anything about changing BIOS (course they probably don't want you monkeying with it).
Some systems automatically recognize a vide card and no BIOS changes are needed, while others do require disabling the the integrated graphics in the BIOS.
You could just try following the directions Omnisome provided above. If so, remember to set a restore point before you do and then it should be easy to go back. Also save a copy of the old driver if you can in case you need to manally restore it, or see if it is available on the DVD that came with the mobo.
Alternatively, you might ask Biostar for directions using their E-Support: