I start of a reply. Simms & Cod need a bit of memory, HDD Space and AGP Graphics card and if Simms 2 DirectX 9.
Ideally 384MB Memory minimum, watch you have plenty of HDD space free and Graphics card (Not Intergrated) ideally 128MB though 64 would be ok but nowadays 128MB is sensible.
Like a Nvidia FX5200 128MB DDR Memory AGP x8 minimum upto so not to overdo things FX5700LE.
Ideas can be found at my local haunts
But please make sure you can disable any onboard graphics/VGA before purchasing a new card.
As I said before many answers will arrive possibly saying ATI card, either do the job but for stabilty and hassle free I recommend Nvidia chipset cards.