The Acer W500 is a great little tablet PC. Accessing the BIOS under the default Windows 7 can be difficult due to the speed of the system. Accessing the BIOS under Windows 8’s Hybrid Boot can also be extremely difficult. Here’s how to force the tablet to pause so that you can log into the BIOS or use an external USB drive to boot the device.
First, try the combination of Power + Windows button, then F2.
Second, interrupt Windows with a hard shutdown (hold Power for 5 seconds). Try the Power + Windows + F2 button combination again. This time, you might have extra time since Windows believes there was a system error needing analysis and repair.
Third, disable Hybrid Boot under Windows 8, which can be found under Control Panel> Change what the power buttons do> Change settings that are currently unavailable. Then try the Power + Windows + F2 combination again.
Credits for this fix come from the TabletPCReview Forums.