@Regi67If a new save will load in a clean folder but your old one won't, it's entirely possible that the existing save is corrupt in some way. It's also possible that some content present in your existing save isn't installed in the new folder, but usually missing items are replaced and the save loads anyway. One thing you could try is loading a backup save in the clean folder instead. Even if you don't regularly make backups, the game does, keeping the second-to-last save in your saves folder as well. This one will have a .backup extension (so if your main save is SunsetValley.sims3, the backup would be SunsetValley.sims3.backup). If you delete the .backup and rename the save (i.e. SunsetValley1.sims3), it will be available to load at the Main Menu. It's a good idea to make a copy of this backup as well, so that you can revert to it if something else goes wrong.
It should also be said that your system is somewhat underpowered to be running TS3. You only have 6 GB RAM, which is technically enough for the game and your OS, but not much else. It's a good idea to restart your computer before playing, and to make sure nothing is running in the background besides essential Windows functions and Origin, if you need it to play.
More important is that you only have an integrated graphics card, and not a particularly strong one at that. I'm not sure which packs you have installed, but Pets and Seasons, and maybe even IP and ITF, might be more than this card can manage. (This could also change with the in-game seasons—snow and hail are particularly hard to render—and whether you currently have any pets in your active family, particularly long-haired ones.) You can help your card by turning down the graphics settings somewhat (particluarly water and high-detail lots—I have those on "mirrors only" and 2, respectively), but there's only so much stress it'll be able to handle.
This is, I guess, a long way of saying that your computer might not be able to handle running TS3 the way you'd like. I'm not sure if this is why your existing save isn't loading, although it's certainly possible, but you could run into a situation where your system has trouble loading and maintaining existing games, once they progress past a certain point. Again, this depends on which packs you have installed. But if you're having trouble running the game on a regular basis, or existing saves often fail to load, you might need to uninstall some packs in order to keep playing on this computer.