Hey Matusalem!!!
9400 GT s******cks!!

Also 512 MB too few nowadays (1 GB/1024 MB at least is good... )
sry but true, it is a faaaar too old and outdated and of course too weak (since x4xx GT ) card to handle PR well... should only work ALMOST fine on EVERYTHING/every graphic setting on lowest setting... :/
Sry 4 you, also, 64 bit Windows (version "7" in this case) only makes sense if more than 3,8 GB RAM... so, also highly suggest you, upgrade RAM to 4 GB and get THIS graphic card at least:
Starting with cheapest:
Amazon.com: NVIDIA GeForce GTS 450 1536MB/1.5 DDR5 PCIe Dual DVI Video Card mini-HDMI & HDCP: Computers & Accessories (ONLY 2 LEFT in stock!!! GET it! Price down to 83 $ from 110 $ !

And you basically COULD even overclock it of you need! For PR though it will be FAR enough!

)
OR (but is moar expensive AND weaker power

so actually fail:
Asus NVIDIA GeForce 640 2GB DDR3 PCI Express 3.0 Graphics Card: Computers : Walmart.com )
So REALLY try to ship the amazon card to you!!! (IF you really are from brazil

)
I have GeForce 9600 GT (also 512 MB) in my 2nd pc, the older one (new one is GTX 570), I of course overclocked it back in the days to get SOME decent performance in PR on Full HD resolution. Also have 2 GB RAM there, but Win XP and Core2Duo E6300 (2x 1.86 GHz xD lol, MoBo permitts overclocking sadly, otherwise I'd run it on 3 GHz!

)
I hope this helps you good...

Good luck!