Actually there is no need to uninstall and re-install. I got this quick fix courtesy of the Shrub guys. It's not as complicated as you might think;
You'll have to run the "Regedit" tool. This can be daunting to some, but just follow these instructions exactly and you'll be ok.
Click "Start", then "Run" then type "Regedit" and click "OK".
Click the plus sign next to the "folder" named HKEY_LOCAL_MACHINE.
Click the plus sign next to "Software"
Click the plus sign next to "Activision"
Click directly on the folder named "Return to Castle Wolfenstein"
On the right side of the Regedit Window double-click the "Version" value and then just type 1.31.
Click "OK" then close "Regedit".
Now download and run the full 1.33 Patch. This will allow you to install the 1.33 patch over the 1.4 update.
Viola! Instant 1.33 Wolfenstein!
Yavol! Hello, Hallo, Hey, Hi, Hello!