To be honest, it sounds like your 'p' key is stuck or has something stuck in it. All it takes is a small bit of debris, food, liquid, etc., to cause a key to malfunction. So I would turn it off and check that first. Should that not do it, then try the following...
NOTE: If you need to type in a password to even get into Windows to do the following, make sure you attached an external keyboard first, to get past the password. Then try the following... just make sure you disconnect the external keyboard while the system is reloading.
1. Uninstall the keyboard driver.
2. Reboot the computer (without reinstalling the driver).
3. When it restarts, it should reinstall the driver on its own.
If this doesn't work, you may wish to try...