Reinstall my computer before install of AVG

I need to know how to get my computer back to the way it was, before AVg suggested I change things that was to help me, instead I lost base programes and controle. It is like my whole computer was revamped, and deleated on structions it would help my computer. Now can not find or access base progreams evn for my printer. If it is in computer some place do not still know how to access it, I am told it was either moved or deleated or became crupted? I want to have my origineal operation and setting back, and well not use instrutions from AVG to make my computer faster. When I got slower and does not want to even load up, nor take my password it takes minutes to get past pass word, then I can not use my printer as now it says programe is missing and do not know whaere it went or how to get it back? Everthing is just a mess. And if I take out AVG well it revert to the way it was or am I screwed.