I had to think about this one for a day. Here goes in order of importance:
2+ Gig 533 RAM
--If data has to go to disk when editing you are screwed, max the RAM
P4 EMT 64
--P4 still has an edge in vid processing over AMD due to higher (1066) FSB
--You will have 64 BIT support when it applicaiotns and windows finally become fully stable and available.
--You will be able to upgrade to a dual core P4 eventually, if needed.
HD
--Speed doesn't matter PATA, SATA, 7200 or 10000. When you have to go to HD you are screwed, it is orders of magnitude slower.
--Size does matter. Some recent reviews show that the new mega HD's are slower than the medium sized ones. Put in two HDs. One for the operating system and raw data and a second drive to use for the video processing scratchpad. 2 drives, not 2 partitions!
Video Card - TBD, not familiar with the product lines.
--It must have built in hardware codecs!
--A card intended for video processing (optimized for 2D applications) is what's needed, not a hot gaming card that does 3D very well.
Monitor - 19" CRT
--The LCD monitors have a reduced and distorted color space compared to a CRT so they don't render as correctly. Not as big an issue with video editing like it is with photo work but since it is graphics work I still prefer CRT.
That should come in under $1500 (unless the vid card is an issue, the commercial vid cards used to cost multiple body parts.).