Try the regular uninstaller and then also Rejzor's util which runs in Normal windows mode.
http://rejzor.wordpress.com/avast-cleanup-tool/
Is the D&C directory corrupt ?.....you did copy Mom's data files off to USB HDD ?
@TheKochs: I've tried the Avast uninstaller and literally nothing happens, it brings up the window, I hit Uninstall and it takes me back to desktop with Avast still in the Add/Remove Programs list...might have to just use Rejzor's tool anyway!
Mom's data files are somehow actually here and not corrupt....I may have made a mistake in that regard; her user profile folder IS labelled "name" but all her data is still in it. Maybe it WAS called that before, and I'm not remembering - I don't use her machine very often other than to fix it!
I will back her data up to my USB HDD adapter for now, yes.
I've not heard of Macrium, but I'll have to check into it. I'd need to get a larger backup drive first though, as I don't have one big enough for a full image of her C:/ drive, let along the C:/ drive on my machine!
@Essexboy: I'll try that and let you know....here's hoping it will actually restart normally this time! BUT, before I try it, should I run Rejzor's Avast uninstall tool BEFORE I run OTL considering the usual Add/Remove Programs Uninstaller for Avast isn't working...?