Function key functions - Dell N5010

Normally f keys have wonderful functions. f5 refreshes screen during OS use and f2 makes rename command, f1 starts help etc. While using some programs like MS Office and AutoCAD these keys gain new and very useful functions. Like when you are using AutoCAD f8 turns on and off the Ortho command which is normally used inside another command i.e. when you are drawing a new line... In general, for increasing the functions, there s an "fn" key that is similar to the "shift" key. When we press and hold fn and f-keys, hardware related changes are made. For example, when you press fn+f5 the screen brightness is increased. HOWEVER... with my laptop DELL N5010 the situation is reverse. To enlighten the screen or other hardware related commands, i need to use f keys WITHOUT fn key. That is ok. But when i want to use commands like, refresh, rename etc in windows and osnap, ortho etc in autoCAD, i have to press and hold fn key UNFORTUNATELY. It is so annoying to hold fn key each time i need to use ortho on/off command or osnap on/off command. AutoCAD users must be fully aware that how frequently these commands are used. So, what i wish to ask, how i can change this absurd condition. What i want is to use NORMAL f-key functions without pressing and holding the fn key. As a result, hardware comments together with fn key... If anyone can help me, it will be highly appreciated...

Originally condition is this. When i first used laptop it was as i described above and same applies to another friend's laptop which is also Dell. f key functions require pressing and holding fn button, while hardware related functions can be used by only pressing fn. I want to change this. For windows use it is ok but during AutoCAD and MS Office apps, since i already hold mouse with one hand, pressing and holding fn in addition to the required f-key makes me drive crazy. Need urgent help :)