Black Screen on startup after installing a theme

I was installing a new theme earlier tonight on my desktop. I got an error code when I installed the shell32.dll file but for some reason I chose to ignore it because most errors don't seem to do anything. When I restart my computer and I try to log in, the screen is black and I get an error code. I have fixed a problem similar to this when my explorer.exe file got corrupted. I went to Ctrl+Alt+Del then>Open task manager> and from there I could open chrome and download a new them installer etc but now I can't even open the task manager file because I get another error code. How on earth am I supposed to fix this shell32.dll file and get to my task manager without re-installing windows? Please help me Tom's Hardware!