CPU comparison

The original Core 2 CPUs is more than twice as fast per clock per core than the Pentium 4. That means one of the two cores in the original 1.86GHz Core 2 Duo E6300 (not to be confused with the current 2.8GHz Pentium Dual Core E6300 [thank you Intel marketing ]) has about the same performance as your single core 3.6GHz Pentium 4. Then realize you have a second core of the same speed raring to go. On top of that there's been a round of performance improvements on the Core 2 line that boosted performance on the current crop by another 10-15%.

As for the P4 end of lifespan. Yes, that time came and went when the Core 2 was introduced in July of 2006. When the low end of the new CPU line performs as well as the highest end of the previous CPU line, that era is over.

Right now Intel is looking at nearing the end of the Core 2 line of CPUs. They haven't introduced any top end CPUs for Socket 775 since the Socket 1366 Core i7-9xx series came out last year instead introducing CPUs in the sub $150 range for dual core and sub $200 range for quad core. Now with Intel starting to roll out the Socket 1156 Core i3, i5 and i7 series it pretty much closes the book on Socket 775 within the next two years.