So, my friend told me that going to msconfig and checking the multiple processors button and putting the processors to 4 (my processor is quad core) will make my pc run faster and make my games have bigger fps. The only thing I want to change is the number of processors being used at the startup, nothing else. Is this going to help me or not and can it screw anythng up on my pc?
So, tell your friend he doesn't have a clue what he's talkin about...
If Number of processors in Advanced Boot options is unchecked, windows will use the maximum number of cores that it can during the boot processes. So you cannot set anything higher than Windows is already using.
That setting is meant to be used only for advanced troubleshooting purposes when a know-how wants to use less then the maximum amount of cores. And fiddling with those setting can potentially make your system unstable.
So to sum up: Nothing will got better by checking the multiple processors, and everything could got problematic by checking the multiple processors.