Version compatability

I installed Intellicad v 6.1.16.1 Premium Edition on my new pc, running 
windows xp.
I installed my old pc with Intellicad v 3.3.004 standard edition in my
shop. 
Now thinking I can transfer files from home to the shop, no problem, but
the 
files created or revised on v 6.1 will not open on my old pc with version 
3.3.  I cannot install the new intellicad v 6.1 on my old pc, because it
is 
using windows 98 and will not sup****t the new version, I cannot update the

old pc, because the processor and memory will not sup****t xp.
I wanted to be able to take files from my home to my shop.   I thought all

their advertising says Intellicad files are compatable with all auto cad
and 
others.
I cannot believe that Cadopia did this with their own product,  and there
is 
no way for me to adapt a file for both versions....   sounds like
microcrap 
here to me......  Disappointed with purchase of intellicad version 6.1.
Can anyone help here?    Thank-You

Ray