The computer has become very slow!

Good day. Ordered fumigation of cockroaches and after it would not turn on the computer. I immediately realized that the moron had put in the system unit of poison, because before it everything worked like clockwork, and when I came after the airing the computer will not turn on.More precisely included, but the image was not. Then I removed the graphics card and started the computer from the CPU and it worked, but the computer has become terribly slow. I reinstalled Windows and it didn't help. All possible driver set and still lag. I understand that in the case of the components already, but do not want the new comp to collect. If anyone knows what the problem is and what it is best to replace it please help(