Unsure how to do differential backup

Hi,

I'm imaging up 400GB+ of data (a whole HDD - a Win7 partition, my data partition and the rest of the stuff that Paragon includes when backing up a whole HDD) onto a 1TB USB drive that also has some other content on it. I use the WinPE boot disc from Paragon Drive Backup Pro to do this, and I'm running Win 7 Home Premium x64 (RTM). The backup takes 9-10 hours and always verifies successfully.

It would be really convenient if I could create differential images relative to the base that I've already created. Presumably this would be lots quicker.

However, the only way I can see to create a differential image is under Wizards > Differential. This asks me for the location of my base image (remember that I'm using file view as the archive DB is disabled under WinPE) then asks where to save the differential. I specify my 1TB drive and it says that it needs about 400GB of space, and that the 1TB drive doesn't have enough. If I ignore this and run the backup (I've never let it run to completion/running out of disk space), I notice that in addition to two 'backup partition' entries, it's also planning to merge backup files. I don't want it to merge, I just want to be able to create smallish differential files (say 20GB of data had changed on the HDD) and store them on the 1TB drive. If I wanted to merge them later I could do that, but I don't want to do it now (I suspect the merge is why it wants 400GB+ of HDD space).

I'm not using partition encryption so that can't be the cause. Grateful if anyone could point out where I'm going wrong.

 

Forgot to mention that the WinPE disk is ver 10.0.10.10505_000 - I downloaded it from the Paragon website after entering my login details.