The first I would do is checking the processes of the OS, close any heavy applications like antivirus or graphic design program.
Then check if there are viruses or worms on the computer, clean it if there is.
Check all options on Dolphin setting except Enable Cheat (if you don't use it), use OpenGL plugin, check Native resolution if you have too, turn off MSAA or reduce it.
Then check if there are viruses or worms on the computer, clean it if there is.
Check all options on Dolphin setting except Enable Cheat (if you don't use it), use OpenGL plugin, check Native resolution if you have too, turn off MSAA or reduce it.