advantages of 865 over 845.
1.Better memory architecture
2. support for all S478 CPUs. 845 wont support prescotts with 800Mhz FSB.
3. Dual channel DDR400, this makes all difference. 845 dosent support Dual channel DDR400
4. 865 by default dosent have PAT, only 875P chipsets do but ASUS has implimented function called Turbo mode which is basically what PAT does on 875. Gives nice boost in performance.
5. better onboard graphics than 845, of course if you are planning to use it. Otherwise get 865PE chipset motherboard and not 865G
6. Whatever CPU you use 865 will perform better than 845 chipset motherboard.
And yeah what nikhilesh has told is correct but he could have used better language
but he is telling the truth.