performance not up to par

I use Windows NT 4 on a dual Pentium 3 500 stand alone computer with 256 MB SDRAM, a Pinnacle-Miro DC50 video capture card attached, 4gig e-ide system hdd, and a 9gig barracuda scsi hdd video. I run Adobe Premiere, Photoshop and After Effects exclusively, no other software is installed. My device drivers are up to date and so is my Nt service pack. But video processing and rendering time is just about the same as a single Pentium 2 300 (my old video setup). It is slower when image filters are applied. I feel shortchanged because this dual processor machine is performing like a single processor machine. I’d like to speed up my render time and get more work done.