Krunk wasn't much help. I've tried some of the steps before. I do not have system restore turned on so there's nothing to restore to. I do not have an original CD as none was shipped with the laptop. Several other methods I tried had me remove all the old updates from when it was working so the system currently shows no updates have ever been applied, though they clearly have.

The windows update and repair tools...Done method 1, does not work. Method 2, the update errors out when trying to apply. "Windows Update Agent Installer encountered unrecoverable error." I went through all the Method 3 steps, and still not working.

I used SpeedyShare as you recommended, and uploaded CBS.log
CBS.log

Good question. Other than being stupid, I turned it off because my computer has an 86.5 GM hard drive. After using it for a few months I had only 3GB of free space. Almost 40GB were found in restore points so I deleted them all and haven't turned it back on.

Since step 3 not working may be caused by something else, I'm running a couple on-line virus checkers. Trend Micro house call and Symantec. Of course, I do have my own Sophos running all the time, so who knows what I'll find. I will give Microsoft help a shot in the morning and call them. I'm in Oregon, Pacific Time.

Steven, running the findstr /c:""[SR]"" %windir%\logs\cbs\cbs.log command...do I run that and then repost a cbs.log or do I run the command, and then run sfc/scannow again after your command? Thank you.

Well, time to close this case. My Thinkpad has an OEM version of Windows Vista Ultimate so Lenovo will not release a DVD of Windows to me. Microsoft, this morning, spent 3.5 hours logged into my computer trying to get Windows Update to work and they could not get it going. Lenovo says go back to an original configuration and recovery DVD. Will probably suck it up and do that as no alternative is available at this point.

I think I have found what causes this error. I had previously manually updated rather than waiting for automatic updates so the updates I am getting Windows Update Error 80070490 on are already installed when you check the list of installed updates - followed by a long list of "failed".

Good luck

Look here Update error 80070490

It may help.

I don't know why you dug this ancient thread.This thread is from 2008 year.Some people have realy archaeological capacity LOL.

This error have many various options and there is no easy answer,each case is individual.

First I suggest to run sfc tool and readiness tool and don't be lazy and want to view what is CheckSur.log and in SFC report.Even you have any corruptions in CBS,WinSxS in mostly cases Readiness Tool can't fix them automatically and there is no such kind of tool -you have to do that manually

If there are some errors in SFC report and in CheckSur.log you have to analyze and fix them manually,if there are not errors than probably any 3p programs disturb installation.
In this case you could try install updates/service packs from Microsoft Download Center,reset Windows Updates or rid of program which cause problem -of course always is problem to guess which one it is
Krunk4Ever! » Blog Archive » Windows Update Error: 80070490 - After eliminating all other possibilities, the one remaining-no matter how unlikely-must be the truth.
apart 3p sucurity software also other programs may cause problems e.g Deamon Tools,Alcohol 120,USB Safely Remove and probably many others (check also user comments not only main article) +wide google of course

There is also special MS fix which could help you if you have no errors in SFC report and CheckSur.log and still you have no clue what cause your problem
Error message when you install an update by using Windows Update on a computer that is running Windows Vista or Windows Server 2008: "0x80070490"

Sometimes you have to analyze full CBS log (not only SFC report)
How to overcome error 0x80070490 when installing updates in Windows Vista/Server 2008 - Andreas Klein - Site Home - MSDN Blogs

I have only one objection to @andrekl post:

His reset.bat script does not restore original permissions but give much more permissions for Users and Administrators than they have defaultly -this fix has been created for XP but in Vista default permissions are completely different,much more subtle and for security you shouldn't apply this - if you really suspect issue with permissions you should

-uninstall all 3p security software
-try both tools to verify permissions
1)MS Fix It-> How do I restore security settings to the default settings?
2)Rizone Security Restore http://www.rizone3.com/?download=secres.zip
-If really nothing help:use Process Monitor to diagnose issues with permissions