Lag in The Sims 3

Unfortunately, its not the game's fault, its your PC. Your specific IGP (Integrated Graphics Processor), an AMD Radeon HD 6310, has no dedicated memory at all -not good! It doesn't really meet the game's minimum system requirements. Adding EPs just makes things worse as each one added increases the min sys requirements, some more than others. Your friend's PC, and your older one, likely has a stand-alone GPU, a Mobility Card or a more powerful IGP.

Source: http://www.notebookcheck.net/AMD-Radeon-HD-6310.40952.0.html

The AMD Radeon HD 6310 (or perhaps also called ATI Mobility Radeon HD 6310) is an integrated graphics card in the Zacate netbook processor. It is based on the same graphics core as the ATI Mobility Radeon HD 4330 but without any dedicated memory. Furthermore, it features the newer UVD3 video processor.

The 3D performance of the HD 6310 should be beneath a HD 4330 due to the missing dedicated graphics memory (shared memory only). Gaming performance should therefore be similar to a Nvidia ION or Intel HD Graphics graphics card. In our tests the 6310 was only able to run low end games like Fifa 11, Sims 3 and Star Craft 2 single player in lowest detail settings fluently. More demanding games like Risen or Call of Duty series were not playable.

 You can try some of the suggestions here to squeeze a bit more out of the PC:

Lags & Freezes

My PC has high performance Nivida Proccesor still lags as well. I believe its the coding not my comp. Im using Nivida suggested settings as well and have dedicated 3gb of ram to your game.