We're going to need more information than that. That could be a Socket 423 Pentium 4 which uses Rambus RIMM modules, which are very expensive and hard to find these days. It could also be a Socket 478 Pentium 4 which would use DDR RAM, which is somewhat less expensive and hard to find these days.
Try running a program called CPU-Z on that computer and post the results, it should tell you which Pentium 4 you have, which motherboard you have, and the type of memory your computer is using.
I had thought that the Willamette cores never hit 1.9Ghz, but apparently they did.