Hello, I'm having trouble getting an update to install on a client PC. The update is KB2393802 and it fails with code 0x800B0100. This is on a Windows 7 Pro 32-bit machine. As recommended in the help for this error code, I downloaded and ran the System Update Readiness Tool. The CheckSUR log showed corruption of some MUM and catalog files and reported a list of 'unavailable repair files'. I then followed the instructions in the article below to extract the missing files from the downloaded update to the required folders within %windor%\Temp\CheckSUR. http://technet.microsoft.com/en-us/library/ee619779(WS.10).aspx I then re-ran CheckSUR and got the following log: ================================= Checking System Update Readiness. Binary Version 6.1.7601.21645 Package Version 11.0 2011-04-13 21:14 Checking Windows Servicing Packages Checking Package Manifests and Catalogs (f) CBS MUM Corrupt 0x800F0900 servicing\Packages\Package_2_for_KB2393802~31bf3856ad364e35~x86~~6.1.1.1.mum Line 1: (fix) CBS MUM Corrupt CBS File Replaced Package_2_for_KB2393802~31bf3856ad364e35~x86~~6.1.1.1.mum from Cabinet: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab. (fix) CBS Paired File CBS File also Replaced Package_2_for_KB2393802~31bf3856ad364e35~x86~~6.1.1.1.cat from Cabinet: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab. (f) CBS MUM Corrupt 0x800F0900 servicing\Packages\Package_4_for_KB2393802~31bf3856ad364e35~x86~~6.1.1.1.mum Line 1: (fix) CBS MUM Corrupt CBS File Replaced Package_4_for_KB2393802~31bf3856ad364e35~x86~~6.1.1.1.mum from Cabinet: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab. (fix) CBS Paired File CBS File also Replaced Package_4_for_KB2393802~31bf3856ad364e35~x86~~6.1.1.1.cat from Cabinet: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab. (f) CBS MUM Corrupt 0x800F0900 servicing\Packages\Package_for_KB2393802_RTM~31bf3856ad364e35~x86~~6.1.1.1.mum Line 1: (fix) CBS MUM Corrupt CBS File Replaced Package_for_KB2393802_RTM~31bf3856ad364e35~x86~~6.1.1.1.mum from Cabinet: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab. (fix) CBS Paired File CBS File also Replaced Package_for_KB2393802_RTM~31bf3856ad364e35~x86~~6.1.1.1.cat from Cabinet: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab. (f) CBS MUM Corrupt 0x800F0900 servicing\Packages\Package_for_KB2393802~31bf3856ad364e35~x86~~6.1.1.1.mum Line 1: (fix) CBS MUM Corrupt CBS File Replaced Package_for_KB2393802~31bf3856ad364e35~x86~~6.1.1.1.mum from Cabinet: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab. (fix) CBS Paired File CBS File also Replaced Package_for_KB2393802~31bf3856ad364e35~x86~~6.1.1.1.cat from Cabinet: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab. Checking Package Watchlist Checking Component Watchlist Checking Packages Checking Component Store (f) CSI Manifest All Zeros 0x00000000 winsxs\Manifests\x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.20826_none_5978b89a766d479e.manifest x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.20826_none_5978b89a766d479e (fix) CSI Manifest All Zeros CSI File Replaced File: x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.20826_none_5978b89a766d479e.manifest From: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab (f) CSI Manifest All Zeros 0x00000000 winsxs\Manifests\x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.16695_none_6bfbed8a157ebb3f.manifest x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.16695_none_6bfbed8a157ebb3f (fix) CSI Manifest All Zeros CSI File Replaced File: x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.16695_none_6bfbed8a157ebb3f.manifest From: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab (f) CSI Manifest All Zeros 0x00000000 winsxs\Manifests\x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.16695_none_58a26a2b5d8954ed.manifest x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.16695_none_58a26a2b5d8954ed (fix) CSI Manifest All Zeros CSI File Replaced File: x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.16695_none_58a26a2b5d8954ed.manifest From: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab (f) CSI Manifest All Zeros 0x00000000 winsxs\Manifests\x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.20826_none_6cd23bf92e62adf0.manifest x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.20826_none_6cd23bf92e62adf0 (fix) CSI Manifest All Zeros CSI File Replaced File: x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.20826_none_6cd23bf92e62adf0.manifest From: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab (f) CSI Manifest All Zeros 0x00000000 winsxs\Manifests\x86_microsoft-windows-r..gistry-trustedtypes_31bf3856ad364e35_6.1.7600.20826_none_849fd3eba8a7b88a.manifest x86_microsoft-windows-r..gistry-trustedtypes_31bf3856ad364e35_6.1.7600.20826_none_849fd3eba8a7b88a (fix) CSI Manifest All Zeros CSI File Replaced File: x86_microsoft-windows-r..gistry-trustedtypes_31bf3856ad364e35_6.1.7600.20826_none_849fd3eba8a7b88a.manifest From: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab (f) CSI Manifest All Zeros 0x00000000 winsxs\Manifests\x86_microsoft-windows-r..gistry-trustedtypes_31bf3856ad364e35_6.1.7600.16695_none_83c9857c8fc3c5d9.manifest x86_microsoft-windows-r..gistry-trustedtypes_31bf3856ad364e35_6.1.7600.16695_none_83c9857c8fc3c5d9 (fix) CSI Manifest All Zeros CSI File Replaced File: x86_microsoft-windows-r..gistry-trustedtypes_31bf3856ad364e35_6.1.7600.16695_none_83c9857c8fc3c5d9.manifest From: C:\Windows\CheckSur\v1.0\windows6.1-7601-x86-cab4.cab (f) CSI F Mark Missing 0x00000002 f!ntdll.dll x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.20826_none_5978b89a766d479e (fix) CSI F Mark Missing CSI Registry Item Repaired Wrote x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.20826_none_5978b89a766d479e\f!ntdll.dll: ntdll.dll (f) CSI F Mark Missing 0x00000002 f!ntoskrnl.exe x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.20826_none_6cd23bf92e62adf0 (fix) CSI F Mark Missing CSI Registry Item Repaired Wrote x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.20826_none_6cd23bf92e62adf0\f!ntoskrnl.exe: ntoskrnl.exe (f) CSI F Mark Missing 0x00000002 f!ntkrnlpa.exe x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.20826_none_6cd23bf92e62adf0 (fix) CSI F Mark Missing CSI Registry Item Repaired Wrote x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.20826_none_6cd23bf92e62adf0\f!ntkrnlpa.exe: ntkrnlpa.exe (f) CSI F Mark Missing 0x00000002 f!ntoskrnl.exe x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.16695_none_6bfbed8a157ebb3f (fix) CSI F Mark Missing CSI Registry Item Repaired Wrote x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.16695_none_6bfbed8a157ebb3f\f!ntoskrnl.exe: ntoskrnl.exe (f) CSI F Mark Missing 0x00000002 f!ntkrnlpa.exe x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.16695_none_6bfbed8a157ebb3f (fix) CSI F Mark Missing CSI Registry Item Repaired Wrote x86_microsoft-windows-os-kernel_31bf3856ad364e35_6.1.7600.16695_none_6bfbed8a157ebb3f\f!ntkrnlpa.exe: ntkrnlpa.exe (f) CSI F Mark Missing 0x00000002 f!ntdll.dll x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.16695_none_58a26a2b5d8954ed (fix) CSI F Mark Missing CSI Registry Item Repaired Wrote x86_microsoft-windows-ntdll_31bf3856ad364e35_6.1.7600.16695_none_58a26a2b5d8954ed\f!ntdll.dll: ntdll.dll Summary: Seconds executed: 300 Found 16 errors Fixed 16 errors CSI Manifest All Zeros Total count: 6 Fixed: CSI Manifest All Zeros. Total count: 6 CSI F Mark Missing Total count: 6 Fixed: CSI F Mark Missing. Total count: 6 CBS MUM Corrupt Total count: 4 Fixed: CBS MUM Corrupt. Total count: 4 Fixed: CBS Paired File. Total count: 4 ================================= All looked good. I then ran Windows Update to install the update in question and it seemed to install ok but prompted me to reboot. After reboot, Windows Update says the update still needs to be installed. Attempting to install the update at this point results in the same failure as I began with. Running CheckSUR again produces the same, seemingly good, log but the install/reboot/failure cycle just repeats. I have also tried renaming the Catroot2 folder and renaming all oem*.* files as recommended in other MS support articles. I don't know what else to try. Any assistance to resolve this will be greatly appreciated. Thanks, David