I had the same problem, boot wait was disabled, it booted straight into Windows without checking for F2 key. Windows was crashing and couldn't even load safe mode which led to an unusable system.
I succeeded with a rather drastic solution: I powered off the laptop, unplugged it, removed the battery, and REMOVED THE HARD DRIVE. This made it impossible for it to load windows on boot, allowing me to get into BIOS setup with F2!
It is safe to power on a laptop without a hard drive. Just don't install or remove it while on, and/or when battery or line power is connected!
I don't truly know if this is related to your question or my solution, but when I changed the boot order from 'windows boot manager' to 'hdd0', Win7 was able to...