The best move is to unplug the 7 drive to see 8 as a stand alone on the second and press the F key assigned(F4, F8, F11, or F12 usually sometime the DEL key is used on portables however) to bring up the boot device menu in order to select the 8. Someone here refers to that as bios managed dual booting.
Thatt seems to be far less problematic then replacing 7 mbr entries with those for 8 being the newer version and problems seen when booting into 7 from the 8 boot options. Lately I have been hear about a few other bugs in the retail besides drive errors ending being seen however.
For those running Gigabyte boards the AppleCharger.sys file mainly for seeing hand helds like Fruti Company IThis or IThat recharged is put back by MS with Win 8 after Gigabyte had already removed that particular driver from their updates!
The person discovering that one ran the Autoruns utility found at the TechNet Sysinternals downloads to isolate the problem it was causing with shutting 8 down and see a hanging black screen instead.