How would you go about switching from uefi to legacy bios/boot? Would you have to reinstall windows? Can you use the hidden partitions for this? Would you need a windows install disk?

Outside of significant hacking wizardry, you'd need to get the different BIOS from the motherboard/computer vendor. Unlikely.

You can change the setting in the BIOS usually.

I think if the disk is in GPT format, it may not boot in Legacy Mode on some hardware which may require a reinstall. On some BIOSes, when you change to legacy it won't show the HDD as a bootable device, or you may get a BCD error.

^{I interpreted his question as "I want to reflash my BIOS and get rid of this new UEFI stuff". Toggling between legacy mode kinda does that...I guess? I thought that it was still UEFI but in "legacy mode" when you did that as opposed to actually swapping out for a different BIOS. I'd be interested to know how that works and if it is consistent across vendors.}

You are right tain, you can interpret it that way. If you dig down to the bottom, there are 2 types UEFI 2.3.1 firmware and BIOS. We call "it" (the menu) the BIOS still. UEFI BIOS (sic) usually has legacy support in it and can be changed in the Boot section or CSM. You can choose if you want devices to boot in UEFI or Legacy mode. Some systems let you enable both, but I prefer to use one or the other...

Now the amount of systems that would let you replace the entire firmware with an actual BIOS rather than a UEFI is going to be limited. For example, the Intel 6 series boards you can find some that have either a BIOS or UEFI. Intel coincided adding UEFI to their boards with support for 3rd gen CPUs. You can find board REVs here: (3^rd Gen-Ready AA#s)

http://www.intel.com/support/motherboards/desktop/sb/CS-033076.htm

But I am unsure if you could dump the BIOS from the old rev and put it on the new rev. I think for most people's concerns is that they can disable UEFI boot in the BIOS (and secure boot or whatever else) if they have the option. Then, for all intents and purposes, they have normal "BIOS" ...

As mentioned, all "BIOSes" are different and some may not operate the same way as others.

Great post. Thanks buddy!

By the way, can someone explain briefly what this "secure boot" thing is?

http://blogs.msdn.com/b/b8/archive/2011/09/22/protecting-the-pre-os-environment-with-uefi.aspx

That's really informative, thanks.