How do you guys feel about sub OS's

I was thinking about making a sub operating system. That includes some programs that i been working on.
If you dont know what a sub os is. Its a operating system that need another operating system to run. (well i pretty sure thas what it is).

do you guys think they that Sub Os's are a waste of time to make.
or are there actually good ones out there anywhere.

Is this a "just for the heck" of it project, or do you have a need to create this?

What language would you be using?

i'm doing it for just for the heck of it.

i want to to use vb net but i might switich to c#