Hey guys. So I just installed MorrowindOverhaul 3.0, but not easily. There was much strife and pain involved, but I eventually managed to figure everything out. Now, I wanted to help out anyone who has the same problems I had.
1. Download Morrowind Overhaul from here: http://www.moddb.com/mods/morrowind-overhaul-sounds-graphics/downloads/morrowind-overhaul-sounds-graphics
after you download this (which should take 30 to 70 minutes) open it with a zip program, such as WinRar, WinZip or 7Zip.
2. Extract all the files with whatever zip program you so choose to C:\Program Files (x86)\Steam\steamapps\common\Morrowind
3. Open MOInstaller. Follow the steps until you get to the EXE optimizer, you will (I can guaruntee this) get a notification that says it cannot find the Morrowind.exe file. That is because this folder does not exist with the Steam version of this game. But no worries! I found someone on the internet who scripted this file. Here is the download link for it:http://www.filefactory.com/file/ahb35f3/n/morrowindsteamfix_zip
In order to download this, you have to create a FileFactory account (that is the website it takes you to.) But no worries, that only takes a moment. When you download the file, use 'Slow Download,' uncheck the box under it that wants you to use the FIleFactory download manager.
4. Once you have downloaded the file from FIleFactory, open it it with a zip file program, as you did with the MorrowindOverhaul files. Rename Morrowind-fixed.exe to simply Morrowind.exe. Extract it to C:/Program Files (x86)\Steam\steamapps\common\Morrowind
After you do this, move on to step 5.
5. You're almost done! Just follow the steps until you get to end, and you're done! You have successfully installed MorrowindOverhaul 3.0. Congratulations. Now go play your newly updated game.
Note: If you have any problems here, please say so in the comments below. I will do my very best to help you out.
Edit: I haven't played Morrowind in a long time, and as a result, I haven't been keeping track of MGSO's updates or current significance. If this tutorial isn't working for you, it may be outdated. If you simply cannot get it to work, I would recommend browsing the Morrowind Nexus for more fantastic mods. There are a couple very helpful mod loaders out there, out of which I would reccomend Wrye Mash. It's a very well thought out mod loader, and once you get the hang of it, it's very easy to use. You can download it from here: http://www.nexusmods.com/morrowind/mods/27588/?
Frankly, you'd probably spend less time finding a downloading 50 different graphics mods than you would spend trying to figure this out. But, if you're one of the lucky people who this worked fine for, congrats!