I have installed slackware 10.0 a few times before. I have been trying to installed and I created my partition with cfdisk and on two separate machines I had problems while coping the files.
After about 25 trials I decided to use fdisk instead and It works!
the small computer with Slackware 10.0 and the top of the line with Slack 11.00 and both systems are installing without problems.
I didn't think I was doing anything out of the ordinary.
Any clues on what I may have done wrong? It just seems a lot easier to use cfdisk but I am puzzled.

I'm not sure what you did wrong. Perhaps you didn't set your root partition to be bootable when you were using cfdisk (just guessing)? I use both fdisk and cfdisk. cfdisk is easier to use. Hey, if fdisk works without errors then stick with that:-)

I always use fdisk and I prefer it to cfdisk, for no particular reason (I think they both do the job)

I don't know why cfdisk didn't work for you - Just use what works, no matter what is supposed to be easier or better.

qtparted might be for you!