An x-ray is only 2-dimensional. A CT scan is essentially a 3D x-ray but is done in slices as you know. To convert the CT scan into 3D, try following the 3D slicer instructions on our forum:
Another free 3D slicer program some of our members have liked is radiantviewer.com. A third option, if you have a disc reader, is to copy the info on your disc into your computer hard drive & create a Dicom.zip file with it then upload it onto dicomlibrary.com which may have options to convert it to 3D (not totally sure about that though).