Effects on system after removing Zeroaccess?

Hello! Pardon me, I'd like to request some help cleaning off my mother's laptop. A few weeks back, I removed Zeroaccess from her computer, after reading many of the threads from the knowledgeable folks here. I thought everything was fine, scans didn't detect it or any other malware/viruses, but things were sometimes...odd. When installing a game, or occasionally when performing other tasks, the computer would freeze up (not responding) and disk write was at 100% according to resource monitor. Other times things seem fine. I'm not expert enough to know if this could be fallout from Zeroaccess or anything else, any help would be appreciated...thanks again for your time!

- Kathleen