what software are you installing after initial install...
open task manager and see if any of the background processes are eating up all the cpu...
particularly 1s like CMD and com surrogate.
if something using a constant 20% or there about cpu without the system looking like its doing anything. try killing that process and see if things speed up. (dont worry the most that will happen doing this is a forced system restart if you close something you shouldnt)
also try disabling file and folder indexing
then open folder options and enable always show icons never thumbnails...