Window suddenly became very slow

After a recent update of some windows 'enhancement' file,my windows 8 became very slow,in all aspect,slow start up,slow shut down,slow opening app,slow opening folder,it takes about 5 minute to total shut down before I can switch it on again,I dod not install a lot of program inside my computer,only firefox,a MCU programmer and a MCU basic compiler and norton antivirus,that all,what wrong with my computer