well if your Pentium 4 has little pins sticking out of the bottom of the processor chip, then no since new dual core motherboards use the LGA775 socket, and old Pentium's used the socket 478 but you can check.
and most motherboards now use DDR2 memory, but if you use DDR memory then no you wont be able to use the memory you have, but, if your using DDR2 now then yes you could use the same memory