i recently installed windows 8.1 preview and i cant use my other graphics card (sli) through nvidia control panel but when i just had 8 i worked just fine please tell me what i can do if not tell me how to go back to windows 8 again.

Try this 8.1 driver:

http://www.nvidia.com/object/win8-win7-winvista-32bit-326.80-beta-driver.html

http://www.nvidia.com/object/win8-win7-winvista-64bit-326.80-beta-driver.html