hiya mate, I had this problem,
Go to the install directory for metro, in there look for the nvidia physx installer,
Install this, reboot the machine, if you have steam on auto start, close steam properly and re-open,
If you still get the error, do a search on your machine for the physx.dll or whatever its called and copy it to your install directory for metro,
That should sort the problem out, I have the same problem every time I re-install it
Let me know how you get...