So, before you call me a newb, I already know. I messed up majorly. I have a Radeon HD 7850, I unplugged my r7 240 and plugged in the HD7850. I only had one power connector to power the fan, so I plugged it in and everything was working ok. I booted it on, noticed that one fan wasn't spinning and I knew it was because the other power connector wasn't plugged in. I saw a connector and plugged it in(while my computer was still on... ye I know.), and I didn't notice that the same connector branched off of the hard drive's connector. I don't know if this is making sense.. but, the computer instantly shut down, and wouldn'treboot. I removed the GPU and unplugged it, and plugged in the old R7 240. I tried to reboot it, and now the hard drive isn't being recognized. I disconnected the connectors to the hard drive and reconnected them, still nothing. It's giving me an error 'PXE-61' when I try. If I can fix this, I'm never touching computers again.