Why am I lagging? (Empire & Napoleon Total War)

[navywolfx]

I had tried the demo but I had severe lag when doing so. These are the requirements:
OS: Windows XP/Vista
Processor: Intel Core 2 DUO @ 2.2 GHz / AMD Athlon 64 X2 4400+
Memory: 2 Gb
Hard Drive: 15 Gb free
Video Memory: 768 Mb
Video Card: nVidia GeForce 8800 / ATI Radeon HD 3800
Sound Card: DirectX Compatible
Network: Broadband Internet Connection for Online Multiplayer
DirectX: 9.0c

These are my specs on dxdiag:
OS: Window Vista Home Premium (6.0)
Processor: AMD Turion Dual-Core RM-75
Speed: 2.2 GHz
Memory: 2814MB RAM
Video Card: GeForce 8200M G
Direct X: Version 10.0
Free space: 194 GB
Video Ram: 1.4 GB

I am a noob at computers, so can you please note out where I should upgrade my computer and recommendations? Thank you so much. (:

[mroilfield]

go to www.canyourunit.com and see if the games are in the list then have the site scan your comp and it will tell you if your meet the requirements and if not what is keeping you from meeting the requirements.