Win 7 SP1 fails with 800B0100 error along with 3 other updates

Right, will try that.

Just noticed this is the same 50202 fix I've used a couple of times. Hasn't worked then either.

Will go through those and see if any help.

Nope, all failed.

Here are the error lines from the most recent attempt.

2011-10-30 09:25:20:319 1300 1d08 DnldMgr Error 0x80070003 occurred while downloading update; notifying dependent calls.
2011-10-30 09:25:20:360 1300 1d0c DnldMgr Error 0x80070003 occurred while downloading update; notifying dependent calls.
2011-10-30 09:25:20:402 1300 1cfc DnldMgr Error 0x80070003 occurred while downloading update; notifying dependent calls.
2011-10-30 09:25:20:458 1300 1d00 DnldMgr Error 0x80070003 occurred while downloading update; notifying dependent calls.
2011-10-30 09:25:20:538 1300 1d4c Agent *************
2011-10-30 09:25:20:538 1300 1d4c Agent ** START ** Agent: Finding updates [CallerId = AutomaticUpdates]
2011-10-30 09:25:20:539 1300 1d4c Agent *********
2011-10-30 09:25:20:539 1300 1d4c Agent * Online = No; Ignore download priority = No
2011-10-30 09:25:20:539 1300 1d4c Agent * Criteria = "IsInstalled=0 and DeploymentAction='Installation' or IsPresent=1 and DeploymentAction='Uninstallation' or IsInstalled=1 and DeploymentAction='Installation' and RebootRequired=1 or IsInstalled=0 and DeploymentAction='Uninstallation' and RebootRequired=1"
2011-10-30 09:25:20:539 1300 1d4c Agent * ServiceID = {7971F918-A847-4430-9279-4A52D1EFE18D} Third party service
2011-10-30 09:25:20:539 1300 1d4c Agent * Search Scope = {Machine}
2011-10-30 09:25:24:022 1300 1d4c Agent WARNING: Failed to evaluate Installed rule, updateId = {2BB8F7BC-D043-419E-B1D3-337501FB7BB7}.101, hr = 80242013
2011-10-30 09:25:26:510 1300 1d4c Handler FATAL: UH: 0x800b0100: EvaluateApplicability failed in CCbs::EvaluateApplicability
2011-10-30 09:25:26:518 1300 1d4c Agent WARNING: Failed to evaluate Installable rule, updateId = {F9164872-3E27-4410-B4FC-038814549BB1}.100, hr = 800B0100
2011-10-30 09:25:26:933 1300 1d4c Handler FATAL: UH: 0x800b0100: EvaluateApplicability failed in CCbs::EvaluateApplicability
2011-10-30 09:25:27:464 1300 1d4c Agent * Added update {40336E0A-7B9B-45A0-89E9-9BD3CE0C3137}.101 to search result
2011-10-30 09:25:27:464 1300 1d4c Agent * Added update {213F0C0E-2AFB-423F-B8A0-B1289FDA5C1B}.102 to search result
2011-10-30 09:25:27:464 1300 1d4c Agent * Added update {5DA03162-868E-4567-80A2-D046B3FB1B09}.100 to search result
2011-10-30 09:25:27:464 1300 1d4c Agent * Added update {FDA58512-32F3-4A5D-A5C4-05A193E037D4}.103 to search result
2011-10-30 09:25:27:464 1300 1d4c Agent * Found 4 updates and 70 categories in search; evaluated appl. rules of 1389 out of 2778 deployed entities

Something is obviously very wrong so in the absence of any solution I suppose we must consider an virus infection.

Run Malwarebytes in Safe Mode to see if anything shows up.

Malwarebytes : Malwarebytes Anti-Malware is a free download that removes viruses and malware from your computer

Other than that, I think it is Microsoft Support as Jan suggested or a clean install of Windows and carefully updating a few updates at a time rather than a whole bunch all at once.

Yeh, slowly preparing it for a clean install while doing these attempts.

Will try the scan in a moment.

OK, it'll be interesting to see if anything shows up.

Found 10 so far and still going, should be finished in the next half hour. Quite annoyed my AVG didn't pick it up :/.

On a side note, can you recommend a good combination of free security software? Been using a combination of AVG + Spybot for the past 5-10 years. Not really checked to see how well they have been keeping up with other security firms.

Many of us use Microsoft Security Essentials alongside Malwarebytes.

Microsoft Security Essentials | Protect against viruses, spyware, and other malware

AVG seems to have fallen by the wayside these days.