Since the Asus G73SW ...

is a high end i& laptop a half hour to start up does seem a bit much.

It does have the Sandy Bridge chipset and there were quite a few problems with that chipset so I will point you to some specific information since you didn't indicate how long you have had it.
http://www.notebookcheck.net/?id=45596

You never indicated whether or not it has booted slow since day one or if it started slowing down and you re-installed. If the later is the case it is quite possible that you have failed to install the proper drivers the manufacturer installed at the factory. It is possible that you updated some of the drivers and strange to tell, sometimes a new driver does not work as well on a system as the older driver.

It could also be malware causing holdups in the starting of Windows or possibly you have "optimized" the system and disabled or removed services the laptop requires to function properly.