Realtek HD Audio: The Realtek audio chipset is also very comonly found in Macs. Unfortunately, again, the installation requires you to do some tinkering: Go to Guru3D and download the latest Realtek HD Audio drivers. Make sure not to get the MSI installer, we need the extractable ZIP/EXE format -- you'll see why. Download and extract the file. Go to "Device Manager", double-click on "Sound, video and game controllers" and then "Realtek High Definition Audio". Go to the "Driver" tab, click "Update Driver" and point it to your downloaded directory. Hit "OK" to install these drivers! If you don't follow these steps and just go with the regular installer, you'll hear no audio out of your speakers -- it's likely one of those weird little Windows on a Mac issues.
Step 7: Enable AHCI or not?
I've talked about the missing AHCI drivers before. Thanks to a crippled BIOS emulation and some weird decisions on Apple's part, the storage controller runs with legacy IDE drivers instead of AHCI drivers, which makes for a noticeable loss in performance.
I've read pretty much everything there is to read on this issue and tested all the hacks that help you enable AHCI on your Mac or MacBook. Be warned:
While, yes, AHCI can be enabled, it's a dirty hack that changes the Master Boot Record. If anything goes wrong, you'll spend a couple of hours reinstalling both Mac OS X Lion and Windows so be sure to create a complete image, before you do this.
All hacks out there work only on Macs with Intel chipsets. Nvidia Chipsets are not supported.
There's a good chance that you'll be stuck with a longer shutdown time (1-2 minutes) and with a non-functional sleep mode! Hibernation continues to work fine.
If these (possible) issues don't bother you or are less important than the possible performance gain, I'd suggest you give it a go. Obviously, I don't have to remind you to create an image of both your Mac OS X and Windows partition (see below) first, before you move ahead with changing the master boot record (MBR).
Start Windows 7 and fire up "regedit". Go to the key "HKEY_LOCAL_MACHINE_ System\CurrentControlSet\Services\msahci". Double-click on "Start" and change the value from whatever it is to "0". Repeat this step with the following keys (if present):