I had trouble installing the newest patch 1.4. It kept giving me the error "1628: Failed to complete installation." If anyone else is having this problem (maybe its only a xp64 problem), here is what I did to fix it:
1. Open the Administrative Tools control panel.
2. Open Local Security Policy.
3. On the left side of the window that opens, highlight the Software Restriction Policies folder by left clicking on it once.
4. Go to the Action menu and press New Software Restriction Policies.
5. Now, in the left side of the window, some icons should have appeared. One of them is called Enforcement, and it's icon should look like blue 1's and 0's.
6. Right click it and press properties.
7. In the window that opens, check the "All users except local administrators" radio button.
Hope this helps some of my fellow COD:WaW friends!
Thanks Aeronut & DrWorm. That worked for me. I'm a XP64 user too