sound problem and keyboard problem please help

i dont realy know much about my computer. i know that it is a gateway comuter.my keyboardad speakers were working fine then i rebooted my computer a couple days ago. now it says the acpi cannot install and now my keyboard and speakers arent working. i am using the on screen keyboard. this has happened to me before and all i had to do was d/l it from download.com. the only problem is i dont know what program i downloaded. my device is working,and my speakers r connected, but on the device manager it says i have no device,& i dont have a cd. if u can please help i would relly appreciate it. thank u.