Windows XP crashes at Shutdown (Error Code 0x000000C2)

I'm having problem with a new Windows XP computer crashing when I shut it down. It doesn't crash every time it shuts down but it does very often. When it crashes, this happens almost inmediately after pressing Shut Down (Start > Turn off computer > Shut Down).

At first this would have Windows XP restart automatically but when I disabled automatic restart on system failure I receive a Blue Screen instead. A typical log entry in System Log would be this one:

Event Type:      Error
Event Source:      System Error
Event Category:      (102)
Event ID:      1003
Date:            31/01/2008
Time:            02:26:58 p.m.
User:            N/A
Computer:      ABAL
Description:
Error code 000000c2, parameter1 00000007, parameter2 00000cd4, parameter3 142b0403, parameter4 e4f34df0.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 53 79 73 74 65 6d 20 45   System E
0008: 72 72 6f 72 20 20 45 72   rror  Er
0010: 72 6f 72 20 63 6f 64 65   ror code
0018: 20 30 30 30 30 30 30 63    000000c
0020: 32 20 20 50 61 72 61 6d   2  Param
0028: 65 74 65 72 73 20 30 30   eters 00
0030: 30 30 30 30 30 37 2c 20   000007,
0038: 30 30 30 30 30 63 64 34   00000cd4
0040: 2c 20 31 34 32 62 30 34   , 142b04
0048: 30 33 2c 20 65 34 66 33   03, e4f3
0050: 34 64 66 30               4df0    

I have also opened the minidump files with Microsoft Debugging Tools for Windows, and all of them say: Probably caused by : win32k.sys

I have posted last 6 minidumps at http://rapidshare.com/files/88868567/Minidump.zip

I would like to know what I would need to do now. Windows XP has already been properly updated with Windows Update.