It's annoying when they come on because they're loud, but that's what they're there for. Your computer has fans designed to keep the CPU cool when it's operating at capacity. Like any language, it's possible to write code that uses lots of resources, and there isn't a generic way to prevent software from being written inefficiently, or from using the available system resources. Flash isn't a video player or conferencing software, although you can write those things using Flash technology. Other people write software in ActionScript, which they compile to bytecode, which we interpret and do all of the low-level processing stuff for - like allocating and tracking memory, rendering pixels to the screen, etc.
