So this morning I installed Avast Free Antivirus on my computer. And hours later when I turned my computer back on I can't get into Windows. Startup is fine, but once I put in my PIN or Password into my account, the screen goes blank and I have turn shutdown my computer by holding the power button. I restarted and everything and tried to make it work but I can't get past the sign in screen. If anyone knows a possible solution please write back, thanks.