I have a copy of both EQ4 and EQ5 and some of the accompanying books. I've not had the energy/clear headed-ness to use the program to anything near it's capacity. That said, if you want the EQ, I would suggest ebay or Amazon. I got the EQ4 for a few bucks and I thought it was just the book, had the disc with it!
They issued EQ6 and EQ7 practically right on top of each other so there may be lots of copies around now.
If you join The American Quilters Society you can get a really nice discount on software if you buy it thru them, the discount is especially great if you buy 6 or more books or software packages.