I have a high-end computer and my Arma 2 works well - I can put the settings to the max with 3000m visibility in relatively big battles without problems. However, I recently installed OFP (GOTY patched with 1.96) and for some reason, it lags like hell even when I put the settings to very low.
I have Win 7, Athlon X6, PowerColor Radeon HD 5870 1GB and 4GB of RAM. My drivers are up to date.
If anyone knows what's going on, it would be appreciated.