The P4, which is not the best is fine for today's sims. I have friends who still use P4's with a good AGP GPU and I still have that sort of system as a backup rig and while they are old systems they can run today's sims without much trouble on mediumish settings at a lower resolution, 1.5gb ram is fine too.
Upgrading to a 3850 will make your gaming much more enjoyable and give you much more needed performance.
Upgrading to a 3850 will make your gaming much more enjoyable and give you much more needed performance.