when changing harware, there can be many (seemingly unexplainable) issues. Usually it has to do with the simplicity of windows and that it is setup for a specific environment of hardware and changing it without first notifying the system (removing drivers) can have odd and catastrophic effects on the functionality of your system. Another issue is the removal of hardware can damage your memory (RAM), but if only a few dim's on the memory are damaged, then it may take a certain amount of usage until the corrupted memory is used OR specific actions which use the specified (damaged) memory.
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