OK. I think I've got this sorted:
berelinde: EasyTutu or Tutu v4?
Bgp: EasyTutu
berelinde: good, then I have some basic knowledge and am not going to give you completely useless information
Bgp: I don't have Tutufix.
berelinde: irrelevant. Tutufix isn't connected with Lade Jarl's Tutu GUI in any way
Bgp: Lade Jarl's Tutu GUI gave an error message when attempting to install into BaldursGateTutu directory
berelinde: that isn't good. It should install easily. Keep in mind that that mod is packaged with a *very* old copy of WeiDU, so it is going to have to update itself, which means you're going to have to run setup-TutuGUI.exe twice.
Bgp: Lade Jar's Tutu GUI installed cleanly into the BG2 directory.
berelinde: that's good. I would expect it to. I don't understand why it didn't go into your Tutu directory cleanly, though.
Bgp: I get the BG2 Menu in both Tutu and BG2.
berelinde: I would expect you to get the BG2 Menu in Tutu, since you were unable to install the Tutu GUI there, but I'm puzzled by what you say about your BG2 start menu not changing. You should see a stone-motif start page.
Bgp: Now what? (you didn't actually say that yet, but you will, sooner or later)
berelinde: Would you please post your WeiDU log for your BG2 installation? I want to see if you did, in fact, install the mod there. You can open the file in your BG2 directory marked WeiDU.log with any text editor, like Notepad, and copy and paste the contents into your thread. I'm not done yet. One more paragraph.
berelinde, continued: In your Tutu installation, you will find a file labeled setup-TutuGUI.debug (or something like that). You can open that with any text editor. Do you see the words "Stopping installation because of error. Rolling back to previous state." anywhere? If so, could you post a paragraph or two on either side of those words? If not, how about "File not found. Stopping installation."? You aren't going to post the entire debug file, because it contains information for all your other mods, too, and I'm just interested in the Tutu GUI. You're going to read through it looking for something that looks like an error message.
While you're doing that, I'm going to open up setup-TutuGUI.debug on my machine and see what it should look like if it went just fine.