Here is the link to the K-1 firmware page:
Latest PENTAX K-1 Firmware Update : Software Downloads | RICOH IMAGING
- click on the I agree button and start the download.
- find the file on your computer, most likely in the downloads folder but might be elsewhere depending on your setup it will be named: k1_v143.zip (the .zip could missing if you do not have show suffix turned on on your machine)
- the file is a .zip compressed file and the firmware update must be extracted first, so right-click and select "extract all"
- the default settings will create a new folder that contains the firmware file
- the actual firmware file will be named fwdc228b.bin again the .bin might be missing unless you have show suffix turned on.
- now copy this file to an SD card. If your card has been used it will have a DCIM folder on it. DO NOT put the .bin file there, just put it in the root directory.
- now put your card in the K-1. MAKE SURE YOU HAVE A FRESHLY CHARGED BATTERY
- the card needs to be in slot #1 to work
- press the menu button and turn on the camera
- the camera will display the current version and the version on the SD card
- using the arrow keys select the start button and press OK
- the camera will blink 'updating' and then COMPLETE when finished.