I made a math program that ask math question for kids age 9-12

at the end i have a rich text box that displays their answers

I wrote this program ona win 2000 box, in the rich text box i have a couple vbtab statements, when i run it on a 95 or 98 box sometimes the tabs do show and sometime they don't,
what could be a reson for this. I have tested it on many machines
thanks