Fixing a laptop that freezes, Bristol, UK

I have a laptop that freezes, and I don't think it's a lack of memory, I think I mistakenly deleted something useful when I did a cleanup. I tried restore point and failed, so I upgraded from Win7 to Win10 hoping that would cure the problem but it didn't. I have run all obvious things like defrag and fixing registry errors etc through Advanced SystemPro. The laptop can run for hours minutes without freezing, and using different programmes. Once frozen I cannot close frozen programme on main view but often can from task bar. But after a freeze the laptop doesn't run well and I have to reboot and start again. There is also a very minor outlook issue with an error message, probably unconnected.