From the sounds of it, a hardware issue may be interfering here. RTW will give you the occasional CTD, but nothing like what you experience. Unless you have a massive amount of programmes running in the background, there is no reason for such strange performance issues. Can you check your hardware, specifically your hard drive and video card?

with regards to auto win cheat. When the scroll for the battle pops up, go to the console (usually pressing ~ will do) and type in 'auto_win attacker' or 'auto_win defender', and then opt to resolve the battle automatically. It will result in an automatic victory for the army that attacks or defends respectively.