Good day, I wrote a VHDL code in Xilinx 14.4 for the Papilio One 500k. After successfully generating the bit file, the Papilio Loader is unable to successfully load my board with the bit file. Wondering if the code was correct, I changed the Device package and constraints file to match another FPGA of mine. The code works as it is supposed to. To verify that the Papilio One board is functioning properly, I downloaded the test bit file and loaded the Papilio One successfully using the Papilio Loader with Windows 8.1. The test bit file is perfect. So far I have verified that the code is correct, the Papilio One 500k works properly, the Papilio Loader is also working properly on Windows 8.1 when used with anything other than my bit file and Xilinx is working as it is supposed to with Windows 8.1 since I can load my other FPGA. I did email my Papilio One bit file to someone who has a Windows 7 computer and loading it using the Papilio Loader on their computer. The bit file was able to load correctly and the code worked perfectly. i was wondering if you have come across an issue between Windows 8.1, Xilinx 14.4 and the Papilio Loader. Xilinx and Windows 8.1 have never been an issue when writing code and loading the other FPGA. Is Xilinx on Windows 8.1 unable to successfully write a bit file that the Papilio Loader on Windows 8.1 cannot understand? I found it interesting that the test file (which I do not know how or what program was used to write it) worked perfectly and my bit file is correct if loaded using a Windows 7 but not Windows 8.1. Looking into this issue on the gadget factory website, their are two different webpages that discuss Windows 8 and the Papilio Loader. The older webpage discusses that Windows 8 will not allow the device driver to install and to override this by accessing the terminal. The other, more recent, webpage discusses that Windows 8 has the most up to date and necessary driver to run papilio and to cancel out of the driver installation part. I exited the driver installation when asked instead of accessing the terminal because that was the most recent webpage. My Windows 8.1 laptop is fairly new. I have installed, uninstalled and re-installed the Papilio Loader several times. I know that this explanation is hard to follow. I apologize for that. Thank you for your help.