nonstop backup, cannot configure to use extra space on drive

Hi,

I have a 750GB disk in my system, on which I have a 300GB partition that is used for C:. I want to put nonstop protection on this, using the other 450GB on the disk as the storage for that.
The wizard will not let me do this, it continously says there is no partition that can be used.
I have done this with all 750 assigned to C: (only 190 is used, rest is free), I've done it by shrinking the c: partition to 300GB and leaving the 450GB free.
No matter, no joy. The help documentation is not to comprehensive, it does not explain if I can or cannot use one disk or not, it does not say if I should make partitions and logical drives etc. Acronis does not offer me the chance to talk to someone to resolve this quickly, other than if I sign up to pay $10 to pay for a support call.
I hope this forum can help, otherwise Acronis has me up the creek, and I own multiple licenses.