my motherboard is an ASUS P5VDC-MX and I'm using an Intel Pentium D CPU 3.00 GHz , and the motherboard says that it designed for a Intel Penium 4 processor wirh 800 FSB and core speed up to 3.8 GHz. The motherboard also supports Hyper-threading and is fully compatible with Intel 05B-05A and 04B/04A processors, can anyone tell me the best CPU to get for this motherboard ? It's a 775 pin LGA board.
No. Real world difference between the 3GHz P4 you have now, and the 3.8GHz P4 you said was the max the board could take is rather small. More so if you consider then something even as lowly as the C2D 2180 or 2200 will be faster then that 3.8GHz P4. Toms did an article awhile ago showing even the dual core Atoms beating the P4s. Intel did everything they could to increase the P4s frequency, at the cost of the chip being able to do real work.
You don't need to spend $2k on a new computer. If you have a S775, you most likely have DDR2 ram. If you bought an AM2+ motherboard and Phenom 2 CPU you could have a MUCH faster system for probably less then $200. Just reuse all your old stuff.