Norton came pre installed on my computer and has been a pain ever since I got it. It makes my computer outrageously slow, ie. MS word takes over 5 minutes to open due to lengthly virus scans. Now it seems to be corrupted because when I click on it nothing will open. Last night I tried to uninstall it thinking I could re-install it or something else. The uninstall failed and I tried several times. Then I downloaded the Norton Removal Tool but cannot use it because it is not signed. I get this error message: SYMnrt: Invalid Signature. The file is not signed so it won't run.

See the following Symantec link.

Error: "SymNRT: Invalid signature. This file is not signed so it won't run."

Thank you. I followed the link exactly but it didn't work. I am still getting the same error message.

Just so you know up front, I am fairly new to computers, and generally only answer very basic questions. But, I had a bear of a time getting Norton off of my PC, too. (I have an HP, and Norton was "bundled" throughout the PC when I bought it.

The NRT never worked for me, either, even though it ran (unlike your problem). But this did:

http://www.askdavetaylor.com/how_can_i_ful..._my_system.html
http://www.askdavetaylor.com/how_to_fully_...on_from_pc.html

I did this a while ago; notice that the second link is actually revised instructions to the first link. In fact, the first link that I show has a link within that page to the second link that I show.

Good luck!

EDIT: I knew that it worked when my Windows Security Center stopped reading "You have more than one anti-virus", and changed to "AVG reports that it is up to date and scanning is on".

Before install McAfee, it will prompt to uninstall other antivirus. If you say yes, it will automatically uninstall the former antivirus.
Maybe it is a way.