Hey I need to know how to get rid of the fake ms security essentials ASAP! Before my computer crashes...?

I've tried downloading recommended antivirus software to remove it but it won't let me. I have AVG free, and malwarebytes installed but it won't let me access them. It wiped out ALL of my files, and it won't let me use system restore. It won't even let me get into the registry or pull up task manager, and I'm pretty sure if I try to load the software from a flash drive it will block it. The only thing I'm able to use is the internet...I don't know what else to do, I don't want to bring it in to get it fixed because it's very expensive like $100-$200. I hope my files aren't gone forever, I already lost hundreds or thousands of pictures when my pc crashed, and I can never get them back. There's like only 10 pictures of me left...countless others from vacations, childhood, etc. are all gone. I'm really starting to hate computers right now. Can anyone help? I've been searching for 4 hours on how to fix it and I still haven't found anything that works. I'm not going to give up on searching how to fix it, but I'd really appreciate some advice, It'll save me some time.