This issue occurs if you are using Microsoft .NET Framework 2.0 Beta on your computer. To resolve this issue you must remove Microsoft .NET Framework 2.0 Beta from your computer. To do this, follow these steps:
Print this page, then close all running programs on your computer.
On the Start menu, click Settings, and then click Control Panel.
Click Add or Remove Programs.
Click to select the Show Updates check box.
Click Microsoft .NET Framework 2.0 Beta.
Click Change/Remove, click Uninstall, and then click Next.
Click Yes. You may receive a warning dialog box. You must click Yes to uninstall Microsoft .NET Framework 2.0 Beta, Windows Live OneCare will install the Microsoft .NET Framework 2.0 release version for you automatically.
If there is more than one entry for Microsoft .NET Framework 2.0 Beta, repeat steps 4 and 5 for each entry.
Restart your computer.
After the computer has restarted, you can try installing Windows Live OneCare again.
Do not uninstall Microsoft .NET Framework 2.0, you should only uninstall Microsoft .NET Framework 2.0 Beta. Microsoft .NET Framework 2.0 is necessary for Windows Live OneCare to run and should not be uninstalled.
This installation error may occur if you signed up to be a Windows Live OneCare beta user on the BetaPlace website, but you haven’t received an e-mail message from us inviting you to install Windows Live OneCare. Between 24 and 48 hours after you sign up as a beta tester, you should receive an e-mail message from email@example.com with “Your request to beta test Windows Live OneCare has been APPROVED!” in the subject line. Follow the instructions in the e-mail message to install Windows Live OneCare.