I'm not sure what to suggest without more information. Perhaps you can try to get more information from Python when you're doing the install:
1. Find out if pip has a flag for more verbose output. It probably does, but I'm not sure what it is - check the docs.
2. Print out the exit code that Python returns to the shell after the command has completed. A non-zero value usually indicates a problem. I'm not sure how you get the exit code on Windows, but you can look that up.
Have you had difficulty installing other libraries?
1. Find out if pip has a flag for more verbose output. It probably does, but I'm not sure what it is - check the docs.
2. Print out the exit code that Python returns to the shell after the command has completed. A non-zero value usually indicates a problem. I'm not sure how you get the exit code on Windows, but you can look that up.
Have you had difficulty installing other libraries?