The Help page on moving the folder says, "...choose a location on the same hard drive as your operating system. Dropbox won't work correctly if the Dropbox folder becomes inaccessible, which can happen if it's located on an external drive that gets disconnected."
It also says, "...the Dropbox folder must be available when your computer boots and before the Dropbox desktop app starts. "
What if I want to move it to an internal drive other than the OS drive? I do not know the exact power-up sequence but would an internal drive normally be visible by the time Dropbox comes up?
I have dropbox in my D drive but it keeps getting disconnected and when I try to reinstall the app it tries to install in C drive - not enough room for files - and there is no option to choose location of dropbox files. This keeps happening monthly.