1. If you're lagging and you have securom - disable it (securom doesn't work with Windows 10), and use a noCD hack.
HOW-TO: Removing Securom and a noCD hack
2. If you have more than dual cores - throttle the CPU Count back to 1 or 2.
HOW-TO: Throttling the CPU
3. If it's still lagging and you have a load of CC in game - try using the CFF Explorer to increase the amount of RAM that the game can use if you have a bucketload of RAM (Sims maximum is set at 2G).
Tutorial for using CFF Explorer
4. You've done all these and you're still lagging?
Defrag your PC, and run checkdisk.
5. Reduce your CC - you've got too much.