Well, let's see... if you flash your BIOS with the Wii's BIOS, then not only will your computer be completely FUCKED, but you will have done all that for nothing...
The Wii has specific hardware that your computer does not. Does your computer have the exact model Bluetooth, WiFi, DVD drive, SD card reader, and NAND reader that the Wii does? Didn't think so.
You need a computer "7" times more powerful because you are EMULATING the hardware AND software of the console. Want to figure out what I'm talking about, here's an example.
Take a computer that will run Windows 98, just over the max specs. Let's say a 1GHz processor, with 512Meg RAM, and intergrated video. Now, take VirtualPC, and try to run another copy of Windows 98 on it. Yea, that VirtualPC copy of 98 is going to be SLOW AS HELL. But why? Your computer meets the specs of Windows98! Why would the EMULATED Windows98 be so slow? Because your using alot more resources when using 2 OS's.
When you run your NES emulator, your running a program that is the equivilent of every chip and program running on the NES. I know, it's not much, but that's why everyone and everything can run an NES emulator at this point. It's not a lot! The core NES processor runs at 1.79MHz (PAL/Australian at 1.66MHz). The TI-89 graphic calculator runs at 10/12/16MHz (depending on the exact model number)... so, even at the low end, it's over 4x more powerful than an NES!
Now, take the Wii. 729MHz core processor, 243MHz GPU (graphic processor). Yea, that's gonna be difficult to emulate on current computer systems.
Even the Playstation 1 is still not 100% emulated. There are glitches in audio/video, and some games won't work unless you have special addons, and hacks.
It's a very difficult process to emulate any console after the SNES (which still has SOME problems, very very very few, but still some).
If you have any more questions, feel free to ask!