What operating system are you using?
If windows, is it a 32 or 64 bit operating system?
You have photoshop cs5?
It is windows 7 and I'm not sure what my operating system is but when I open Photoshop it opens the 64 bit and not the 32 bit and yes I have photoshop CS5.
Well windows 7 would be the operating system and if the 64 bit version of cs5 opens, then you have a 64 bit windows 7.
There should be a pdf file with instructions if you downloaded it from here:
You can install the picture package plugin into the 64 bit version of photoshop cs5 as long as you use the 64 bit plugins.
If you look on your All Programs list in the windows start menu, the Adobe Photoshop cs5 shortcut without the (64 Bit) after it should be the 32 bit version of cs5.