Welcome to our party Blackie.
KVCD is NOT a codec, its a way of mpeg encoder-settings to get the best out of encodings according to quality and compressibility.
So thats not a codec like Xvid or Mjpeg. We use known encoders like TmpgEnc, CCE, and others which do allow the integration of i.e. the notch mpeg matrix which allows to compress encodings more and this can be made by for example these mentioned above encoders.
A duron 800mhz, no matter how many RAM do you got, .... I assume its very difficult to reach the realtime encoding speed rate. But speed depends primary on your desired resolution you want to encode to.
So do enter the main portal
www.kvcd.net and on the right side you'll find a lot of guides which can explain you the whole KVCD workout.
And in case of further questions ... we stay here and give you a hand.
Inc.