Step 1: Check background programs. 
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 Disable firewalls or other Internet browser programs that can  affect the Internet connection. The following programs can affect the connection  to the Windows Update site and I suggest you remove or disable them:  
  
 McAfee firewall
 Norton Internet Security
 Zone Alarm Firewall
 Panda firewall
  
  
 Step 2: Delete the CatRoot2 folder
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 A: Stop Cryptographic Services: 
  
 1. Click Start, click Run, type in "SERVICES.MSC" and press Enter.  
 2. Double click Cryptographic Services, and then click Stop (if it  has been started). 
  
 B: After stopping Cryptographic Service, please delete the  "Catroot2" folder: 
  
 1. Locate the "C:\Windows\System32\" folder. 
 2. Delete the Catroot2 subfolder in System32. 
  
 Note: I am assuming your Windows Vista is installed in C:\Windows.  
  
 C: Re-start Cryptographic Services: 
  
 1. Click Start, click Run, type in "SERVICES.MSC" and press Enter.  
 2. Double click Cryptographic Services, and then click Start.