Error - Kernel Panic

My computer has been freezing for a while now, but today I got an error message which said "You need to restart your computer". When I logged in I got an error message which said "Mac OSX quit unexpectadly"
Anyone know how to fix this?
I've had it since 2006 and it's worked fine up until a couple of months ago

Tue Jun 2 19:26:56 2009
panic(cpu 0 caller 0x001A9C68): Kernel trap at 0x0105607e, type 0=divide error, registers:
CR0: 0x80010033, CR2: 0x16091000, CR3: 0x01487000, CR4: 0x00000660
EAX: 0x00000000, EBX: 0x00000000, ECX: 0x00000000, EDX: 0x00000000
CR2: 0x16091000, EBP: 0x216aa988, ESI: 0x1314f000, EDI: 0x1314f000
EFL: 0x00010246, EIP: 0x0105607e, CS: 0x00000008, DS: 0x01f70010
Error code: 0x00000000

Backtrace (CPU 0), Frame : Return Address (4 potential args on stack)
0x216aa678 : 0x12b4f3 (0x45b13c 0x216aa6ac 0x1335e4 0x0)
0x216aa6c8 : 0x1a9c68 (0x464700 0x105607e 0x0 0x463de0)
0x216aa7a8 : 0x1a038d (0x216aa7c0 0x0 0x216aa988 0x105607e)
0x216aa7b8 : 0x105607e (0xe 0x48 0x216a0010 0x1f60010)
0x216aa988 : 0x1007d1e (0x1314f000 0x301 0x31b 0x1005e5c)
0x216aaaf8 : 0x1008175 (0x1314f000 0x0 0x0 0x0)
0x216aab28 : 0x43e3d6 (0x1314f000 0x0 0x0 0x4cded88)
0x216aab78 : 0x43f381 (0x1062858 0x1314f000 0x4cded74 0x2)
0x216aabd8 : 0x43cfb4 (0x1314f000 0x9 0x216aac20 0x0)
0x216aacf8 : 0x18e4eb (0x1314f000 0x9 0x4cded74 0x2)
0x216abdb8 : 0x12d506 (0x4cded4c 0x4cf05a0 0x0 0x0)
0x216abdf8 : 0x126609 (0x4cded00 0x0 0x78 0x216abee4)
0x216abf08 : 0x198153 (0x216abf44 0x0 0x0 0x0)
0x216abfc8 : 0x1a0977 (0x38b80a0 0x0 0x1a30b5 0x4367000)
No mapping exists for frame pointer
Backtrace terminated-invalid frame pointer 0xbffedfe8
Kernel loadable modules in backtrace (with dependencies):
com.apple.GeForce(5.3.6)@0xfdb000->0x1072fff
dependency: com.apple.NVDAResman(5.3.6)@0x711000
dependency: com.apple.iokit.IONDRVSupport(1.7.1)@0x703000
dependency: com.apple.iokit.IOPCIFamily(2.5)@0x5c6000
dependency: com.apple.iokit.IOGraphicsFamily(1.7.1)@0x6e6000

BSD process name corresponding to current thread: WindowServer

Mac OS version:
9G55

Kernel version:
Darwin Kernel Version 9.6.0: Mon Nov 24 17:37:00 PST 2008; root:xnu-1228.9.59~1/RELEASE_I386
System model name: iMac6,1 (Mac-F4218FC8)