To make sure we're on the same page, you've tried with the new install the following:
1. A fresh Sims 3 folder - No mods or custom content.
2. No game files from previous game.
3. Load game to main menu, and turned off memories, interactive loading screens, and in-game store.
4. Tried to create a new game. --- Is this where it hangs?
If so, try these troubleshooting tips if you haven't done so already.
1. If you're playing the Origin/Digital version of Sims 3 Try disabling Origin In-Game
Open up Origin, Go to My Games. Right click on the game, and select Game Properties, check the box to disable Origin in game, for this game.
Or you can disable it for all games by:
Go to the Origin menu > Application Settings > Origin In Game and make sure it's un-checked.
2. Try playing the game in "Offline" mode -- In the Origin Client, go to the Origin Menu and select Go Offline. -Or- Go to the Options Menu in-game. (lower left hand corner of the main menu) and select Options and go to the Online tab and uncheck Keep Me Logged In.
3. Check your game options. Sometimes lowering in-game graphics options help.
Lower In-game Graphics
http://www.carls-sims-4-guide.com/forum/index.php/topic,20732.msg401802.html#msg401802This below might not help the never ending loading screen, but helps clean up files that are no longer in use.
Run Ccleaner and it's registry cleaner: (Standard Edition is Free)
-- This helps clean up temporary files, internet cache files and other files that are left behind that are no longer being used.
https://www.piriform.com/ccleaner/download -- PC
How to use CCleaner to fix PC issues
http://www.wikihow.com/Use-CCleanerJust curious, what are the specs of your computer? See the link below for a how-to if you're unsure.
How To: Find System Specs - Windows 10, 8 and 7
http://www.carls-sims-4-guide.com/forum/index.php?topic=18902.msg354633#msg354633