To disable the Windows Media Player 7.0 or later automatic update 

use these steps: 

1. Start Registry Editor (Regedit.exe). 

2. Locate the following key in the registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft 

3. On the Edit menu, point to New, and then click Key. 

4. Type WindowsMediaPlayer, and then press ENTER. 

5. With the WindowsMediaPlayer key selected, on the Edit menu, 
point to New, and then click DWORD Value. 

6. Type DisableAutoUpdate, and then press ENTER. 

7. On the Edit menu, click Modify. 

8. Type 1, and then click OK. 

9. Exit Registry Editor. 
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To disable Prompt to Update Yahoo Messenger:
Go into the folder c:\program files\yahoo!\messenger\ and rename 
the file 'yupdater.exe' to something else, such as '_updater.exe'. 
Yahoo! will then fail to find the file and no more prompts!
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To disable auto update of Adobe Acrobat reader:
Delete folder: C:\Program Files\Common Files\Adobe\Updater5
You may also delete updater5 folders in my documents of each user