I'm working with PET data and SPM2 (I'm using SPM2 due to a compatibility
problem in SPM5…). 

I have water data and carbon tracer data. I want to realign the carbon
tracer data to the water data. 
When I do Realign I choose the water pic first, then my carbon tracer pic. 

The question is: should I choose coreg&reslice or coreg only? Would it make
any difference? 

Next, after Realign, I want to Normalize using the SPM-provided PET.mnc as
template, source water pic and image to write carbon tracer pic; and Smooth.

How does my choice of coreg with or without reslice affect my later steps in
the preprocessing? Any other tips on how to handle my data set? Should I
maybe choose Coregister the water and carbon pics instead of Realign?