Mine was only a cheap computer (£400 from MESH - bargain!) so it's not that great, but it runs The Sims 2 without a glitch.
According to system properties:
Operating System: Windows Vista Home Premium SP1
Manufacturer: MESH Computers
Processor: Intel(R) Core(TM)2 CPU, 4400 @ 2.00GHz 2.00GHz
Memory (RAM): 2.00GB
System Type: 32-bit Operating System
The graphics card is only an in-built one, so not great for a lot of games, but it runs every feature on The Sims 2 to the highest option.