Video play modules on Premiere Pro CS4

I just downloaded a trial version of Adobe Premiere CS4 and I'm having a devil of a time trying to get to start: it keeps popping up the error message: "cannot find capable video play modules", and then "Runtime error R6025". The installation of Premiere Pro went smoothly. I'm working in XP SP3. 2gigs of RAM; I've got an NVIDIA GEforce graphics card that works fine.

I've tried:

1) Updating and correctly installing my nvidia drivers, even with the driver that nvidia indicates is compatible with premiere pro

2) Uninstalling (completely, even using CS4 uninstall script (from Adobe) to completely eliminate traces of the just previous installation) Premiere pro trial and then reinstalling it

3) Making sure I've got the lastest DirectX installed

I've wasted literally hours on this problem, and it's quite frankly causing me to lose confidence in Adobe products.

Can anyone help with some suggestions?

Thanks

Jacomo