this laptop is really pushing my buttons. ever since i've bought it, it's been slow. not super slow but enough to make research it. people say that the 5400rpm HDD makes it slow,others say i have to upgrade the 4GB ram, and others also say the i5-7200U processor is meh. so if i do change it to a 7200RPM HDD and add an extra 4GB ram, should the performance be better? can i just do 1 or the other or do i have to upgrade both? please helppppppppp.