Do less demanding games like Crazy Taxi work?
Are there other controllers connected?
Try it with only the wheel connected.
Does the logitech profiler needs to be open while loading the emulator?
No. It runs in the background, but isn't even really necessary as long as pedals are marked combined.
Do I have to configure the settings in the logitech profiler in order for the emulator to work? (only thing I did was to set the pedal to be combined)
No. Even if the pedals weren't set up correctly the emulator should still launch and play...the pedals just won't work right.
Do i have to run as Administrator?I don't know about this specific case, but I've seen a lot of emulator related programs not work because they needed to access some file that the non-administrator didn't have permissions for.
Is there anything I need to configure from the test settings?Like SegaOutrun said, the card reader needs disabled or it will hang at the screen where it searches for it.
The wheel being connected shouldn't make any difference though.
Is there any tutorial to actually configure everything with the logitech driving force GT?For most things there really isn't much to configure.
Model 2 emulator and the recently hacked Battle Gear 4 are the only things I'm aware of that require the pedals to be marked separate.
A lot of older PC games like Outrun 2006 will scroll through the menu uncontrollably if the pedals aren't marked combined. (this can be done under windows game controllers. You have to right click the controller in win7 to get to this option, not sure about

So for the least amount of configuring, set your pedals to combined under Windows Controllers, then create a Logitech profiler profile for the few things that need them to be separate. (I did this backwards and had to create a profile for everything that required them to be combined).
IMO the console emulators each need a profile also for the sake of adjusting sensitivity, saturation, & wheel rotation.