blue screen of death please help me!!

it crashes all the time what is that?

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Dump File : Mini030812-01.dmp
Crash Time : 8/3/2012 1:13:43 πμ
Bug Check String : BAD_POOL_HEADER
Bug Check Code : 0x00000019
Parameter 1 : 0x00000020
Parameter 2 : 0x85226658
Parameter 3 : 0x85226808
Parameter 4 : 0x08360009
Caused By Driver : ndis.sys
Caused By Address : ndis.sys+d913
File Description : NDIS 6.0 wrapper driver
Product Name : Microsoft® Windows® Operating System
Company : Microsoft Corporation
File Version : 6.0.6002.18005 (lh_sp2rtm.090410-1830)
Processor : 32-bit
Crash Address : ntkrnlpa.exe+cdb3f
Stack Address 1 : ntkrnlpa.exe+ed184
Stack Address 2 : ndis.sys+3f58
Stack Address 3 : ndis.sys+3320
Computer Name :
Full Path : C:\Windows\Minidump\Mini030812-01.dmp
Processors Count : 2
Major Version : 15
Minor Version : 6002
Dump File Size : 141.760

If you would be kind enough to supply us the following information, we will be able to help.