The error 'IRQL_NOT_LESS_OR_EQUAL' typically indicates a problem related to memory access, where a driver or process has attempted to access a memory address without proper access rights. The best initial step in troubleshooting this error is to check the RAM, as faulty or incompatible RAM can often be the cause of this issue. Other options listed may be responsible for other types of crash screens or general system instability, but for the specific IRQL error, the RAM is the most probable cause.