Keep getting this windows 8.1 pop up telling me to download/ run this virus system and it does show the Mcafee shield, but I already have Mcafee Livesafe, so don't know if I should do it or if it is a scam?
Moved to General Discussion.
Check your program list in Control Panel > Programs and Features for an item "McAfee Security Scan Plus and if listed, uninstall it.
It's not dangerous, just a nuisance and a security checker that downloads with 3rd party products such as Adobe - anything & many others.
For instance, using the Snipping Tool which exists on all Windows versions from Vista Upwards:
Just change the operating system at the top right if necessary.
Or how to capture a screen image using Paint (applies to any Windows version):
Again change the system at top right if needed. You'll need Microsoft Silverlight installed for that last one to work. It will prompt you.