my rig is shown in my sign. so here is the problem.  
 
my desktop windows, programs, etc. start looking funny after a long use. say 5-6 hrs. n many application fails to start saying they are not win32 application. n on top of that. i cant copy paste anything. usually ill restart, n my pc will work fine again for 5-6 hrs. this started to happen recently, round friday. just yesterday i got my first BSOD. n i found the code. which happen to be
 

 
after reading about it, it seems like memory issues. so i tested my rams with memtest84+ for almost 6 hrs. n not a single error. then, i tested my cpu with torture test of prime (used Blend test). for another 5 hrs. n again no errors shown. so i thought ok, maybe i was imagining things. after i used my pc for 2 hrs n boom, same things happened.  
 
the only new thing i added to my rig was a 120mm fan. which was more than one week ago.  
 
any help appreciated.  
 
yeah, while testing. i was checking voltage levels on speedfan. there was the usual cpu vdroop. n i saw my ram voltage changing. between 1.79-1.77v. knowing my rams are usual ones with 1.8v.
 
yes, my cpu is overclocked. but it is being like this since i got this rig 5 months ago. although my ram are not overclocked. nor the timings are tight. they are very relaxed at 5-5-5-15.  
 
again, HELP ME. lol

Sounds like a memory leak to me.  Set a perfmon to run for 48 hours or something and monitor % memory utilization.  Then view the log after the crash.

^ ok, so u want me to run what exactly for 48 hrs? memtest+? prime? or any other program (which uses ram, coz i have engineering simulators)?

in the log, i've found many errors.
"Event Type: Error
Event Source: Userenv
Event Category: None
Event ID: 1512
Date:  4/21/2008
Time:  9:08:01 PM
User:  NT AUTHORITY\SYSTEM
Computer: NIGHT_WOLF
Description:
Windows cannot unload your registry file. The memory used by the registry has not been freed. This is often caused by services running as a user account, try configuring the services to run in either the LocalService or NetworkService account. If this problem persists, contact your administrator.  

DETAIL - Insufficient system resources exist to complete the requested service.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp."

"Event Type: Error
Event Source: Application Error
Event Category: None
Event ID: 1000
Date:  4/21/2008
Time:  4:56:33 PM
User:  N/A
Computer: NIGHT_WOLF
Description:
Faulting application hfss.exe, version 1.0.0.1, faulting module hfsslib.dll, version 0.0.0.0, fault address 0x000a9068.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 41 70 70 6c 69 63 61 74   Applicat
0008: 69 6f 6e 20 46 61 69 6c   ion Fail
0010: 75 72 65 20 20 68 66 73   ure  hfs
0018: 73 2e 65 78 65 20 31 2e   s.exe 1.
0020: 30 2e 30 2e 31 20 69 6e   0.0.1 in
0028: 20 68 66 73 73 6c 69 62    hfsslib
0030: 2e 64 6c 6c 20 30 2e 30   .dll 0.0
0038: 2e 30 2e 30 20 61 74 20   .0.0 at
0040: 6f 66 66 73 65 74 20 30   offset 0
0048: 30 30 61 39 30 36 38 0d   00a9068.
0050: 0a                        .      
"
Event Type: Information
Event Source: NMIndexingService
Event Category: None
Event ID: 0
Date:  4/21/2008
Time:  9:09:27 PM
User:  N/A
Computer: NIGHT_WOLF
Description:
The description for Event ID ( 0 ) in Source ( NMIndexingService ) cannot be found. The local computer may not have the necessary registry information or message DLL files to display messages from a remote computer. You may be able to use the /AUXSOURCE= flag to retrieve this description; see Help and Support for details. The following information is part of the event: Service started.
"

Event Type: Information
Event Source: Bonjour Service
Event Category: None
Event ID: 1
Date:  4/21/2008
Time:  9:09:17 PM
User:  N/A
Computer: NIGHT_WOLF
Description:
The description for Event ID ( 1 ) in Source ( Bonjour Service ) cannot be found. The local computer may not have the necessary registry information or message DLL files to display messages from a remote computer. You may be able to use the /AUXSOURCE= flag to retrieve this description; see Help and Support for details. The following information is part of the event: mDNSResponder started
.
"
Event Type: Error
Event Source: Application Error
Event Category: None
Event ID: 1000
Date:  4/21/2008
Time:  8:57:47 AM
User:  N/A
Computer: NIGHT_WOLF
Description:
Faulting application core temp.exe, version 0.96.1.0, faulting module core temp.exe, version 0.96.1.0, fault address 0x0000e282.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 41 70 70 6c 69 63 61 74   Applicat
0008: 69 6f 6e 20 46 61 69 6c   ion Fail
0010: 75 72 65 20 20 63 6f 72   ure  cor
0018: 65 20 74 65 6d 70 2e 65   e temp.e
0020: 78 65 20 30 2e 39 36 2e   xe 0.96.
0028: 31 2e 30 20 69 6e 20 63   1.0 in c
0030: 6f 72 65 20 74 65 6d 70   ore temp
0038: 2e 65 78 65 20 30 2e 39   .exe 0.9
0040: 36 2e 31 2e 30 20 61 74   6.1.0 at
0048: 20 6f 66 66 73 65 74 20    offset
0050: 30 30 30 30 65 32 38 32   0000e282
0058: 0d 0a                     ..      

"
Event Type: Information
Event Source: ESENT
Event Category: Logging/Recovery
Event ID: 300
Date:  4/21/2008
Time:  1:38:10 PM
User:  N/A
Computer: NIGHT_WOLF
Description:
MsnMsgr (3036) \\.\C:\Documents and Settings\nightwolf\Local Settings\Application Data\Microsoft\Messenger\sul_syed@hotmail.com\SharingMetadata\Working\database_3EF8_CEC2_F8CE_7823\dfsr.db: The database engine is initiating recovery steps.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
"

and, this is how it starts usually, with things disappearing (display), or strange funny colors appearing. c how the fonts next to the applications in start menu are gone.

First thing I'd do is un-overclock the system. If no change I'd get a memory fan. Somethings getting hot.

thanks.   but i solved the issue. it was bad install for the matroska codecs. and re-installing it. fixed the issue. i just dont know how bad install caused the memory allocation go wrong within window.  
so besically it was all software.