in processes on the task manager i got loads of items running and i dont know what half of them are for infact its at the stage where my pc slows down when im gaming and games keep closing down to the task bar and applications like email take longer to open then normal how can i find out what should be running and what should'nt.

i need help big time pc is being strangled by it all running. plus i have my firewall/anti virus/pest patrol running at all times even if im just online gaming .i never use to have this porblerm with same amount of ram