Somebody knows which could be the reason?

Code:

DRIVER_IRQL_NOT_LESS_OR_EQUAL (d1)
An attempt was made to access a pageable (or completely invalid) address at
an interrupt request level (IRQL) that is too high.  This is usually caused by
drivers using improper addresses.
If kernel debugger is available get stack backtrace.

Arguments:
Arg1: 00000000, memory referenced
Arg2: 00000002, IRQL
Arg3: 00000001, value 0 = read operation, 1 = write operation
Arg4: 85f09234, address which referenced memory

Debugging Details:
------------------

***** Kernel symbols are WRONG. Please fix symbols to do analysis.

MODULE_NAME: nt

FAULTING_MODULE: 804d7000 nt

DEBUG_FLR_IMAGE_TIMESTAMP:  45e54711

WRITE_ADDRESS: unable to get nt!MmSpecialPoolStart
unable to get nt!MmSpecialPoolEnd
unable to get nt!MmPoolCodeStart
unable to get nt!MmPoolCodeEnd
 00000000 

CURRENT_IRQL:  2

FAULTING_IP: 
+ffffffff85f09234
85f09234 0000            add     byte ptr [eax],al

CUSTOMER_CRASH_COUNT:  1

DEFAULT_BUCKET_ID:  WRONG_SYMBOLS

BUGCHECK_STR:  0xD1

LAST_CONTROL_TRANSFER:  from 85f0ed98 to 85f09234

STACK_TEXT:  
WARNING: Frame IP not in any known module. Following frames may be wrong.
f7c4efc0 85f0ed98 85f0effc ffdff000 ffdff980 0x85f09234
f7c4efc4 85f0effc ffdff000 ffdff980 804dbbd4 0x85f0ed98
f7c4efc8 ffdff000 ffdff980 804dbbd4 85f091f4 0x85f0effc
f7c4efcc ffdff980 804dbbd4 85f091f4 85f091e0 0xffdff000
f7c4efd0 804dbbd4 85f091f4 85f091e0 00000000 0xffdff980
f7c4efd4 85f091f4 85f091e0 00000000 00000000 nt+0x4bd4
f7c4efd8 85f091e0 00000000 00000000 00000000 0x85f091f4
f7c4efdc 00000000 00000000 00000000 00000000 0x85f091e0

STACK_COMMAND:  kb

FOLLOWUP_IP: 
nt+4bd4
804dbbd4 ??              ???

SYMBOL_STACK_INDEX:  5

SYMBOL_NAME:  nt+4bd4

FOLLOWUP_NAME:  MachineOwner

IMAGE_NAME:  ntoskrnl.exe

BUCKET_ID:  WRONG_SYMBOLS

Followup: MachineOwner

Thanks in advance.

incorrect or defective drivers, or defective unit related to the drive that is trying to make it work.
What is the brand and model, or the motherboard?

System Info

MBD: Abit AN7 (chipset: nForce2)
CPU: AMD Athlon XP 2700+ (OC: 12.5X, 166Mhz --> 11X, 200Mhz)
GPU: NVIDIA GeForce 6800 128Mb
RAM: 2x Kingston DDR400 (Dual Channel)

DVD: LG
HDD: 2x Seagate Barracuda 120Gb (RAID 0: 240Gb)

PWR: Levicom 430W

Hope this helps...

After setting the _NT_SYMBOL_PATH environment variable in order to solve Wrong Symbols...

Code:

DRIVER_IRQL_NOT_LESS_OR_EQUAL (d1)
An attempt was made to access a pageable (or completely invalid) address at an
interrupt request level (IRQL) that is too high.  This is usually
caused by drivers using improper addresses.
If kernel debugger is available get stack backtrace.
Arguments:
Arg1: 00000000, memory referenced
Arg2: 00000002, IRQL
Arg3: 00000001, value 0 = read operation, 1 = write operation
Arg4: 85f09234, address which referenced memory

Debugging Details:
------------------

WRITE_ADDRESS:  00000000 

CURRENT_IRQL:  2

FAULTING_IP: 
+ffffffff85f09234
85f09234 0000            add     byte ptr [eax],al

CUSTOMER_CRASH_COUNT:  1

DEFAULT_BUCKET_ID:  DRIVER_FAULT

BUGCHECK_STR:  0xD1

PROCESS_NAME:  svchost.exe

LAST_CONTROL_TRANSFER:  from 804dbbd4 to 85f09234

STACK_TEXT:  
WARNING: Frame IP not in any known module. Following frames may be wrong.
f7c4efd0 804dbbd4 85f091f4 85f091e0 00000000 0x85f09234
f7c4eff4 804db89e f6ee2b14 00000000 00000000 nt!KiRetireDpcList+0x46
f7c4eff8 f6ee2b14 00000000 00000000 00000000 nt!KiDispatchInterrupt+0x2a
804db89e 00000000 00000009 bb835675 00000128 0xf6ee2b14

STACK_COMMAND:  kb

FOLLOWUP_IP: 
nt!KiRetireDpcList+46
804dbbd4 837c240c00      cmp     dword ptr [esp+0Ch],0

SYMBOL_STACK_INDEX:  1

SYMBOL_NAME:  nt!KiRetireDpcList+46

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: nt

IMAGE_NAME:  ntoskrnl.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  45e54711

FAILURE_BUCKET_ID:  0xD1_W_nt!KiRetireDpcList+46

BUCKET_ID:  0xD1_W_nt!KiRetireDpcList+46

Followup: MachineOwner

That is a nice setup. No problems come to mind.
However, you do clearly have driver errors, as determined by your post.
It may be that your video graphics card is bad. But if not, you need to go to the NVidia website to download the new drivers. If you have the new drivers, go back to a previous issue of the drivers to test them.