This is the core IWD-in-BG2 conversion. You will also need the fixpack/tweakpack supplement as well.
Version 8 of Icewind-Dale-in-Baldur's-Gate-II, a conversion project to play IWD in the BG2 engine, is now available. This is a joint project, mostly by CamDawg and DavidW with lots of community help.
I'm going to go out on a limb and say that version 8 is recreationally playable (version 7 basically was, and this version should be a big improvement). The usual warnings apply, though: it's a beta, and almost certainly still has some bugs.
To install, you should first download both IWD-in-BG2.exe itself (warning: it's about 20MB) and the IWD-in-BG2 Fixpack/Tweakpack.
The install process is fairly simple (honest).
Run IWD-in-BG2.exe and choose to install it in a new directory. (The default is C:\Games\IcewindTutu, but anywhere you'd install BG2 is fine - i.e., not your Program Files directory.)
On prompting, type in the path to your BG2 install.
After a couple of minutes, you will be prompted to type in the path to your IWD install.
Go and get a cup of coffee, as the rest of the process takes 10-15 minutes or more. About 5 minutes into this process, the end movie of HoW will play. Turn away from the screen and put the sound down, if you don't want spoilers!
Once the install is complete, run the fixpack/tweakpack, install in the same directory as your IWD-in-BG2 installation, and follow the on-screen instructions.
To play, just run bgmain.exe in your IWD-in-BG2 directory.
Note that if you want to create more than one character yourself (rather than playing with the basic NPCs included in the fixpack/tweakpack, or with Kulyok's Icewind Dale NPC mod), you should
save immediately after starting the game
move your savegame folder from the MPSAVE folder to the SAVES folder
3.reload your savegame in single-player mode
You should be able to use the widescreen mod with IWD-in-BG2; you should also be able to use Kulyok's Icewind Dale NPC mod and CamDawg's IWD Item Upgrade and IWD Unfinished Business mods. Other mods that introduce kits and tweaks may also work, but are at own risk currently.