Is this a reinstall of OneCare or a new install? Have you rebooted the PC?
To remove your McAfee software use the appropriate removal tool for your product from here:
http://community.mcafee.com/showthread.php?t=168100
Once you've done that, if OneCare still won't install, try the following:
Clean boot computer.
1. Click Start, click Run, type msconfig, and then click OK.
The System Configuration Utility dialog box appears.
2. Click the Services tab.
3. Click to select the Hide All Microsoft Services check box. (Bottom of the screen)
4. Click Disable All
5. Click the startup tab.
6. Click Disable All. Click Apply, Click Close.
7. You'll be prompted to restart the computer. Click on Restart.
Refer to this Knowledge Base Article for additional Steps.
http://support.microsoft.com/kb/319624
Install OneCare
http://onecare.live.com
If all fails. Contact support.
How to reach support (FAQ) -
http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve
