Acronis Partion Expert?

I have just installed the new (slave) hard drive and would like to partition it for a second OS. My question is, the hard drive should have been formated during the installation, right? So why when I try to partition the new drive (in the Acronis Wizard) it is telling me that I do not sufficient free space and do I want to format the drive. I figured that you would partition first then format second, depending on whether you want a Primary, Extended or Logical sector. If I format the drive wouldnt it set the whole drive to just one of the above, rather than having a choice between the three? Sorry for the long post

Athlon 2.5
1 gig Ram
310 gig HDD
Win XP