1)  Windows update can fail due to many reasons.But as an initial troubleshooting step we can run script givenbelow.

The following script will re-register windows update dlls and recreate software distribution & catroot folder.

 

To run the script please copy the highlighted content and save it as wu.bat.

 

regsvr32 comcat.dll /s

regsvr32 shdoc401.dll /s

regsvr32 shdoc401.dll /i /s

regsvr32 asctrls.ocx /s

regsvr32 oleaut32.dll /s

regsvr32 shdocvw.dll /I /s

regsvr32 shdocvw.dll /s

regsvr32 browseui.dll /s

regsvr32 browseui.dll /I /s

regsvr32 msrating.dll /s

regsvr32 mlang.dll /s

regsvr32 hlink.dll /s

regsvr32 mshtmled.dll /s

regsvr32 urlmon.dll /s

regsvr32 plugin.ocx /s

regsvr32 sendmail.dll /s

regsvr32 scrobj.dll /s

regsvr32 mmefxe.ocx /s

regsvr32 corpol.dll /s

regsvr32 jscript.dll /s

regsvr32 msxml.dll /s

regsvr32 imgutil.dll /s

regsvr32 thumbvw.dll /s

regsvr32 cryptext.dll /s

regsvr32 rsabase.dll /s

regsvr32 inseng.dll /s

regsvr32 iesetup.dll /i /s

regsvr32 cryptdlg.dll /s

regsvr32 actxprxy.dll /s

regsvr32 dispex.dll /s

regsvr32 occache.dll /s

regsvr32 occache.dll /i /s

regsvr32 iepeers.dll /s

regsvr32 urlmon.dll /i /s

regsvr32 cdfview.dll /s

regsvr32 webcheck.dll /s

regsvr32 mobsync.dll /s

regsvr32 pngfilt.dll /s

regsvr32 licmgr10.dll /s

regsvr32 icmfilter.dll /s

regsvr32 hhctrl.ocx /s

regsvr32 inetcfg.dll /s

regsvr32 tdc.ocx /s

regsvr32 MSR2C.DLL /s

regsvr32 msident.dll /s

regsvr32 msieftp.dll /s

regsvr32 xmsconf.ocx /s

regsvr32 ils.dll /s

regsvr32 msoeacct.dll /s

regsvr32 inetcomm.dll /s

regsvr32 msdxm.ocx /s

regsvr32 dxmasf.dll /s

regsvr32 l3codecx.ax /s

regsvr32 acelpdec.ax /s

regsvr32 mpg4ds32.ax /s

regsvr32 voxmsdec.ax /s

regsvr32 danim.dll /s

regsvr32 Daxctle.ocx /s

regsvr32 lmrt.dll /s

regsvr32 datime.dll /s

regsvr32 dxtrans.dll /s

regsvr32 dxtmsft.dll /s

regsvr32 WEBPOST.DLL /s

regsvr32 WPWIZDLL.DLL /s

regsvr32 POSTWPP.DLL /s

regsvr32 CRSWPP.DLL /s

regsvr32 FTPWPP.DLL /s

regsvr32 FPWPP.DLL /s

regsvr32 WUAPI.DLL /s

regsvr32 WUAUENG.DLL /s

regsvr32 ATL.DLL /s

regsvr32 WUCLTUI.DLL /s

regsvr32 WUPS.DLL /s

regsvr32 WUWEB.DLL /s

regsvr32 wshom.ocx /s

regsvr32 wshext.dll /s

regsvr32 vbscript.dll /s

regsvr32 scrrun.dll mstinit.exe /setup /s

regsvr32 msnsspc.dll /SspcCreateSspiReg /s

regsvr32 msapsspc.dll /SspcCreateSspiReg /s

regsvr32 /s urlmon.dll

regsvr32 /s mshtml.dll

regsvr32 /s shdocvw.dll

regsvr32 /s browseui.dll

regsvr32 /s jscript.dll

regsvr32 /s vbscript.dll

regsvr32 /s scrrun.dll

regsvr32 /s msxml.dll

regsvr32 /s actxprxy.dll

regsvr32 /s softpub.dll

regsvr32 /s wintrust.dll

regsvr32 /s dssenh.dll

regsvr32 /s rsaenh.dll

regsvr32 /s gpkcsp.dll

regsvr32 /s sccbase.dll

regsvr32 /s slbcsp.dll

regsvr32 /s cryptdlg.dll

regsvr32 /s schannel.dll

regsvr32 /s oleaut32.dll

regsvr32 /s ole32.dll

regsvr32 /s shell32.dll

regsvr32 /s initpki.dll

regsvr32 /s msscript.ocx

regsvr32 /s dispex.dll

regsvr32 jscript.dll /s

del %temp% /Q /F

del c:\wutemp /Q /F

net stop wuauserv

ren %windir%\system32\catroot2 catroot2.old

cd /d %windir%\SoftwareDistribution

rd /s DataStore /Q

regsvr32 wuapi.dll /s

regsvr32 wups.dll /s

regsvr32 wuaueng.dll /s

regsvr32 wucltui.dll /s

regsvr32 wuweb.dll /s

regsvr32 msxml.dll /s

regsvr32 msxml2.dll /s

regsvr32 msxml3.dll /s

regsvr32 urlmon.dll /s

net start wuauserv

 

2)      Check if WU is working fine. If not then follow next steps

3)      Clean boot the computer

a.Start-Run-Msconfig
b.  Click "Hide all microsoft services"
c. Click "Disable All"
d. Click Apply/OK and restart

4)              Install latest Windows Update agent

http://technet.microsoft.com/en-us/library/bb932139.aspx

 

5)      Below two articles contain common steps which can be followed in WU issue.

http://support.microsoft.com/?id=910337

http://support.microsoft.com/?id=836941

But it’s always a good practice to look for the errors in windows update log  and then troubleshoot it.

6)      To open windowsupdate.log click on Startà Runà type “windowsupdate.log”

7)      To find the error search the log (from bottom)with key word like ERROR,

Eg

2008-06-13          11:08:35:022       1068       d58         AU            # WARNING: Search callback failed, result = 0x80244018

2008-06-13          11:08:35:022       1068       d58         AU            # WARNING: Failed to find updates with error code 80244018

Or

2008-06-13          11:14:11:739       1068       cfc          Service **  END  **  Service: Service exit [Exit code = 0x240001]

Search error code on http://support.microsoft.com and follow the article related to the error to fix the issue.

 

Hope this will help to troubleshoot WU issues J