Yes this is possible.
By default, Office 2003 files open directly in Office 2010/2007 in Compatibility mode, which means that some new features such as Sparklines in Excel or SmartArt in Word or some animations in PowerPoint might not be available or will be greyed out. You will see [Compatibility Mode] after the file name in the title bar.
If you want to retain full compatibility with Office 2003 and don't need to use the new features, leave the file in compatibility mode and save the file as an Office 2003 file (.ppt). Office 2010 should automatically alert you of any compatibility issues when you save it.
If you're sure that you won't need to edit your file in the earlier version again, you have a couple of options. Take a copy of the file first, then either:
- Convert the file to 2010 format: Select the File tab → Info → Convert (this will turn off the compatibility checker)
- Save the file to the new file type: Select the File tab → Save & Send → Change File Type and select the new file type → Save As.