Windows OS is broken. Every version. It has a nasty, faulty filesystem to start with: it has fragmentation problems I've NEVER experienced in any other OS I've used (and I've used a lot!).
It's unsecure, it degrades with use (wich is..just..so stupid I don't want to see it near me never again), why would you want to use such a piece of crap?
Do yourself a favor and install Lubuntu instead. No, NOT Ubuntu, but Lubuntu. It has low requeriments and it will work way better. It's way easier to use, really. My mother is 54 and she uses Lubuntu everyday (she never used or understood Amiga, for example).
Seriously, WHY Windows? Don't be so cruel with yourself.
I've used lots of operating systems as well. NTFS is a fine file system, As to fragmentation yes 15 years ago, (It used to be called checker boarding on Unix and Linux and older OSes)
As to security I've had a vanilla XP SP laptop with no AV software or security patches connected directly to my external router for 3 years now Std XP Firewall on (Which I use for torrent work).
I've never tried Lubuntu. But the same laptop I spoke of used to be Ubuntu 10 for a little while but it kept freezing on boot randomly.
Good luck to your Mum. Sounds like Lubuntu is useful which is the main thing.
I use Windows because I want to do modern things like encode bluray DVDs and Edit and work with high definition video. I can't do that with any other OS and when I can its at half the speed I can with my Windows/Intel rig.