try a system restore to a saved restore point prior to the install. for more than this, we need to know your operating system.
I tried downloading Paint Tool SAI from Softonic.com and it started installing malware on my computer. I used Malwarebytes to get rid of it before it could finish (322 viruses!) but now whenever I start up my computer, the "Are you sure you want to allow this application from an unknown publisher make changes to your computer?" message comes up. The application says it's "prsetup" I usually clicked No but today I decided to click Yes, then when it finished I used Malwarebytes again (Only 9 viruses this time) to get rid of it. But the message still pops up! How do I stop it? I've tried Malewarebytes, CCleaner, and going into my control panel to look for anything I didn't recognize.

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