I have installed the CS on partition D: but I can't locate the ConstructionSet.ini in C:\My Documents\My Games\Oblivion\. When I try to start the CS, I get warnings: Cannot load Astmosphere model, stars, clouds. What am I doing wrong?

are you trying to load by double clicking an esp? thats what typically gives me those errors. the CS can only be started through the exe (or a shortcut).

This happens, if you start the CS with false set shortcut.

Let's say, you Oblivion is in

C:\myOblivion\

Just open the properties of the shortcut and set the path.
First you have the target:

"C:\myOblivion\TESConstructionSet.exe"

Under that, you see another field. The content is the directory in which the target should run and this must be(for this example)

"C:\myOblivion\"

Of course, if you use another path just replace them. If the path isn't set or isn't set correct, you get the error you posted.

If this doesn't help, try to start the CS out of the directory. If you can't do that you should reinstall the CS, I think.

And, as Lady Nerevar said:
Don't double-click on an esp to open it. This normally doesn't work correctly.

And for the ini: It should be created automatically, if you start the CS. Perhaps you have to start it without these problems you posted.
You don't get the errors because of the missing ini. I tried it. The CS starts normally and creates a new ini.

So it depends on how you try to open the CS(or a bad installation).

It also happens if the BSAs aren't in the data directory (you are spanning them across multiple drives for instance) and don't update the construction set ini with the changed file locations.

Bingo! That's my situation. Except I can't locate the ConstructionSet.ini in C:\My Documents\My Games\Oblivion\. Or anywhere else. Since the first run failed, I guess it doesn't create it.
Tried reinstalling. No luck. Set oblivion.ini back to default. Reinstalled. No luck.
:lightbulb: Can someone upload a clean ConstructionSet.ini to tesnexus?
Are their documented switches for the construction set?

The shortcut is fine. I checked and both paths are correct.
I copied the missing BSAs back to the OB folder. Then ran the CS. I didn't get any errors this time. But after I saw the main window briefly, it CTDed. And it still does not create a ConstructionSet.ini in C:\My Documents\My Games\Oblivion\. :brokencomputer:

When I try to start teh CS from Bash v285, I get an error:
OBSE Loader.exe: Can't inject dll.
Process::InstallHook: couldn't allocate memory in target process
Can't inject dll. :banghead:

[Resolved]The file "Oblivion - Textures - Compressed.bsa" is hard coded in the CS! At least on first run. :banghead:
What idiots!