All, Did anyone encounter this? I wasnt able to import the pwo files generated from Winnonlin 5.3 into Phoenix 64 . Instead I could only saved it as binary file in the document folder without ability to use the data. I feel strange why Pheoneix does not support their own files? I checked the HELP and it does say it supports the pwo files though. Any suggestions? Thank you, PKbeginner 
Phoenix platform version 1.3 installs 2 executables: 1) a 64-bit executable named “Phoenix.exe” and 2) a 32-bit executable named “Phoenix32.exe” In order to use files from legacy WinNonlin 4.x or 5.x, you must run the 32-bit version of Phoenix named “Phoenix32.exe”. To do this, one must first create a New Project in Phoenix. Then, use File | Import to import the legacy WinNonlin file(s) of interest. Please refer to the steps below: 1. Select Start → Programs → Pharsight → Phoenix → Phoenix32 (see attached screenshot) 2. Select File | New Project 3. Select File | Import 4. Browse for the WinNonlin 4.x or 5.x files of interest, and then click Open. 5. An import preview screen will guide you through the import process, for example how to handle column headers and units from a spreadsheet. Click Next >> as many times as required and then click Finish. Any WinNonlin files of the format *.pwo, *.pmo, *.pco, *.pto, and *.wsp can be imported into a Phoenix project. Additional details about importing files can be found in the Phoenix application using Help | Contents | Phoenix Basics | Phoenix Functions | Importing data sets. Hope, this helps. Bernd
You can find more information about 64-bit vs. 32-bit in the Phoenix Getting Started Guide, in the section “Phoenix 64 bit Versus 32 bit Version”. Also, after following the above instructions to load a PWO into a project, you can save the project in Phoenix32, and then open the project in either the 32-bit or 64-bit version of Phoenix.
Thank you for the detailed instructions. Very helpful! PKbeginner