Thanks for the replies. I had many more woes since posting this. It was logging me on as a temporary profile. Restarting / signing in again did not cure it. I attempted system restore but it would not let me and I had to use the rescue package to revert to shop bought condition.
Luckily I backed up my important stuff.
Before going nuclear and reverting the system I tried creating a new profile and transferring the things from the corrupted one - it sort of worked but was still unable to either create a restore point or revert to a previous saved one.
I'm guessing advanced system care deleted some important registry item. I feel like I'm walking on eggshells with this system.