Interesting.
My hard drive was replaced last fall (I'm still in mourning) and I'm pretty sure I had to reinstall EQ5 to use my upgrade to EQ6 CD. No EQ7 involved on that PC.
Yeah, I just checked. I did install it.
I guess I didn't even think to try to install 6 without 5. Hopefully, there won't be a next time to check to see if it works.
And there's this:
http://www.electricquilt.com/Shop/EQ6/EQ6upgrade.asp