N73 Big troubles

Please folks can you help me with this?
I have a Nokia N73 and it keeps freezing after 1mn using, i have to turn it on/off every minute and it's making me mad while i'm with someone on the phone. I fromatted the memory phone from the phone itself with some code that i found on the net, but it didn't change much either. Now what I'm looking for is how do i format my memory phone from my pc? And if I do this, will the system files of the phone be erased? If so is there any way to backup the sys files on the pc? because when I open memory phone folder all i see is a bunch of empty folders. I can't stay more than 30secondes in the memory phone because the explorer stucks completely. I tried to install kaspersky mobile security with the installing application from nokia pc suite to see if it's a virus but it stucks too. Please help me I donnow what to do anymore! How can i fix this freezing problem?

I dont know about that exact model but my sister's nokia was horribly slow and occasionally froze, it turned out she had FAR too many text messages on it so the phone didnt have enough memory to operate. (she had over 8,000 messages on it)