I dont know why my phone somtimes hang am using n81 8gb

I have N81 8gb so i put everything on the mass memory directly.(even the msgs). i recieve "memory full" and "carousel/telephone/ sysAp- not enough memory 2 perform" i cant access the camera, clock, cant change the profile or change the time and date.the phone memory has 25MB it says they r used but actually they arent, i tried 2 install an manager application but it doesnt accept since the memory is full while actually it has nothing in use just empty folders which cant b deleted.clearing the cashe memory didnt work nor *#7780#. i even tried the *#7370# but it did not work either. i dont mind losiing everything on the phone or mass memory. i tried updating and reinstalling the software
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