I have just purchased Windows version of Scrivener. All my work so far has been on a Mac. I want to access this file on my work PC. After backing file up to Dropbox, I access it on the Windows platform. I extract all the files. There are two Scriv files within the folder, my PhD file and the Tutorial file. Double clicking either file does nothing. The blue circle appears by my the mouse icon, but when it stops the file does not open. Instead I am brought to the new project screen in Scrivener. Very frustrating!!! 
Do you mean there are two project files (with the yellow Scrivener icon) within the .scriv folder you’re trying to open? That sounds like a sync glitch, and it would prevent Scrivener from correctly opening the project on Windows. Make sure there’s only one project file within the folder, and I’d check too for any other files within the project that may have “conflicted” appended to the name. Dropbox will add that and information about the computer that saved the file when there’s a sync conflict with different file versions.
Just remove the conflicted or duplicate files from the project folder to your Desktop or a new folder somewhere. Once they’re out, you should be able to open the project in Windows, and then you can go through the files you removed in case there’s anything there you need to copy back into the project.
Switching to “Details” view in Windows Explorer may help so you can compare modified dates for the files. Scrivener on Mac will just ignore the extra files, so it’s possible some of them are so old they’re worthless to you.
On Windows the file structure looks different. On Mac, each project seems to be a single file (it’s actually a folder). But on Windows, each project is the actual .scrivx inside the .scriv folder. I suggest you to try opening that file instead.
Thanks for the responses! It was as mimeticmouton said, the two scriv files that were within the one folder were stopping scrivener from opening either. I deleted the older one, and this solved it. Thanks again!