Converting tapes

After a huge battle I seem to have sorted out converting some VHS tapes to data files, but only if I use one particular computer, and set the display screen to 100% at recommended resolution! The same settings don't work on another Windows machine, and the software I'm using doesn't run on the Macs. Now that the the VHS tapes are converted, I've had to switch my attention to some Hi-8 tapes for a friend - I've never had a Hi-8 system myself, and indeed had never shot any video before 2002, and I started with Mini DV tape.