Welcome to AMD community, first I can not help you if the slots are not placed corectly follow these steps they may help you:
Run windows memory diagontics, it will detect issues and help you solve the issues.
If the first method dont help you, run msconfig.exe, select from tabs Boot, press on windows 7, go to adenced options, if the boot are taking an amount of memory clear it, and press ok, apply changes and restart your pc.
If non of above help you reinstall the shipset driver from officel drivers page. If nothing help go to a repair shop and let him correct the positions of slots. Thanks for your question bye.