unable to install from windows update or automatic updates

It downloads the updates, but fails to install them. I have no idea why. i
tried KB555461, re-registering DLL's (as specified from other posts) but
still nada. here's what I get from event viewer

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Event Type: Error
Event Source: Windows Update Agent
Event Category: Installation
Event ID: 20
Date: 8/2/2006
Time: 7:02:56 PM
User: N/A
Computer: xxxxxxxxxxxxxx
Description:
Installation Failure: Windows failed to install the following update with
error 0x80070643: Security Update for Microsoft .NET Framework, Version 2.0
(KB917283).

For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 57 69 6e 33 32 48 52 65 Win32HRe
0008: 73 75 6c 74 3d 30 78 38 sult=0x8
0010: 30 30 37 30 36 34 33 20 0070643
0018: 55 70 64 61 74 65 49 44 UpdateID
0020: 3d 7b 34 32 34 31 42 42 ={4241BB
0028: 43 44 2d 45 41 33 46 2d CD-EA3F-
0030: 34 38 36 31 2d 39 33 35 4861-935
0038: 33 2d 46 42 37 32 33 44 3-FB723D
0040: 38 45 38 32 44 37 7d 20 8E82D7}
0048: 52 65 76 69 73 69 6f 6e Revision
0050: 4e 75 6d 62 65 72 3d 31 Number=1
0058: 30 32 20 00 02 .
------------------------------------------------------------------------------------------------------------------------

and

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Product: Microsoft .NET Framework 2.0 - Update 'Security Update for
Microsoft .NET Framework 2.0 (KB917283)' could not be installed. Error code
1603. Additional information is available in the log file
C:\DOCUME~1\cocoy\LOCALS~1\Temp\NDP20-KB917283-X86\NDP20-KB917283-X86-msi.0.log.

For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp
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I looked at the log and it says almost the same thing as the above. I am
using Windows XP SP2, McAfee Security Center 2005 (Antivirus and Firewall
only), Tenebril SpyCatcher, Windows Defender. Hope you can help.... Thanks.