I see many of you suffered the same way I did after trying repeatedly to install onecare. I tried everything I could find on the Internet and nothing worked until I accidentally found a note to my future self that I had left on my wife's PC a couple of years ago when I was having similar issues on her machine. At that time, I finally broke down and called tech support, and hours later, they gave me a fix. Since I've gotten lots of good advice here before, I thought I'd "give back" - you know, Karma and all. Today, I tried it (deja vu all over again) and it worked perfectly AGAIN!
Hope it works for you too. Below the note the tech guy sent me. I only had to do Step 1; that worked like a charm for me. You should know that I also used the onecare cleanup tool right before and also did a full disk clean and even a defrag immediately prior to doing Step 1 below and then retrying the install. Again, nothing else, and I DO MEAN NOTHING ELSE, worked for me until I tried this:
Step 1: Register wmidcprv.dll
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1. Click Start, click Run, type "cmd" (without quotation marks) in the open box and click OK.
2. Type in the following command and press Enter.
Regsvr32 %SystemRoot%\System32\wbem\wmidcprv.dll
You will receive a succeeded message. Then, test if the issue persists [restart the PC and try the install again]. If the issue persists, please proceed to Step 2.
Step 2: Register WMI components
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1. Please click Run, type "cmd" (without quotation marks) in the open box and click OK.
2. Type the following commands one by one and press ENTER at the end of each command:
cd /d %windir%\system32\wbem
for %i in (*.dll) do RegSvr32 -s %i
for %i in (*.exe) do %i /RegServer
Note: If the Windows Management Instrumentation Tester window appears, this is normal; just proceed and close it.
3. Restart the computer and check whether the issue is resolved.
