What is the source format you are feeding into nero? If you have mpegs that are close to the resolution of vcd (352x240), then it should be pretty quick. I capture to AVI at I think 352x480, then use TMPGEnc to batch process to VCD. A full hour's worth of source files took 5 hours to encode to VCD format on a 1.4 tbird, 512mb ddr, 60gxp, windows 2000 sp2 machine!
I recommend you do not use nero's built-in decoder, the quality is poor. Go the AVI->MPG route with TMPGEnc. You can set the motion precision to high and get output that is very close to vhs.