Thanks to everyone who has responded here, and I appreciate whs's tutorial on scheduling the restore points.
I guess I should divulge "the rest of the story" here, because maybe it is material.
This was on my daughter's VAIO laptop, which, in early December, and then yesterday, was clearly showing signs of malware infestation. Her Firefox would not launch or run properly (oddly, my account, an administrator one, like hers, on the laptop, seemed to browse fine).
Because I was tired and lazy (a bad combo to have while working on a technical problem), I opted to "blast the problem away" by using SR. I had already tried booting into safe mode and looking around for signs of an infection, and that cured nothing.
I was hoping for a restore point in the past 72 hours, since the problem had only begun last night. But my only choices were 12/25 (upon installation of AVG 2012, an upgrade from AVG 2011), and 12/11, and I forget what the 12/11 trigger had been. So 16 days had passed since the last restore.
Once I system-restored, I had to reinstall AVG 2012 and Firefox, which had been updated between 12/25 (the restore point I used) and yesterday. But everything now appears to be running fine.
So first, any theory about why I'd only have 12/25 and 12/11 restore points, and none since? My daughter is not someone who plays around with settings like how often a restore point is created?
Second, short of using the scheduler, is there a way of checking to see if the restore points are going to be created every seven days again?
Finally, and this isn't a topic for this subforum, but I assume that a good Safe Mode scan with Malwarebytes or Super Antispyware is in order?