Cloning question

I have Acronis True Image 9.0,
A year or so ago, I changed my old hard drive to a new one.
I went from 120gigs to 160gigs. I cloned using True Image with
no problem. If I remember correctly, I used the automatic mode.
Worked perfect. I did not want a partition and I didn't get one.
In other words, the 120gigs went to the new one and I had one
partition with 40gigs free. (I know this is not the best way to say
this)
Two weeks ago, on another computer, I changed a 20gig hard drive
out for a 80gig one. I used the Seagate Wizard which was made
by Acronis. (I am pretty sure about that) After I cloned the old
hard drive (using automatic) I ended up with two partitions.
A C drive with 20gigs and a G drive with 60gigs. I did not want that.
I wanted one C drive with 80gigs. I had to get partition software to correct it. When I used automatic, it didn't ask any questions.

Now I want to change my 160gig hard drive for a 500gig hard drive.
I will be using Acronis True Image 9.0 for this one. If I use automatic, how can I be sure that the new drive will one have one partition with 500gigs free? (less of course what is on the old hard drive). I saw a
video showing how to do it using manual selection. But the first time
I used Acronis, I didn't have any problems with automatic.
What am I missing?
Thanks,
Bill