Stuck on Welcome Screen after system cleanup

Hello,
I'm trying to fix my mom's Lenovo B570. I did a disk cleanup, defrag, and ran a full anti-malware scan. After cleaning off 122 malware items, I restarted the laptop for it to take affect. After entering her password, it's stuck on the welcome screen. Even my dad, who's been in IT for 30 years, can't help me. I've done a forced shut down, but that didn't work and I can't bring up the task manager.