clean the HDD then.
I wonder why you need 2 hours, I remember the installations I did being a lot quicker.
Maybe you could try installing from a usb drive, which is a lot quicker/quieter... the only catch is that you might need some time to learn how to do it
I admitt I never had to install from the DVD, because I can't stand the slow speed and noises and Win7 allows for install from other means.