Cannot Drag and Drog PDF Files

PDFCreator 1.5

Windows XP
Office 2003

I need to combine multiple PDFs into a single file but for some reason on this new installation I cannot drag and drog PDF files into the PDFCreator window. I can drag and drog JPG, DOC or other files but for some reason PDF file are not allowed.
I can add them via the Document->Add menu but it’s not nearly as easy to use.
This feature works fine on the Windows 7 install I did at the same time.