For a number of reasons, I thought my system had been compromised, so I installed Malwarebytes and avast, and uninstalled AVG and turned off Windows Firewall and Defender. I hope I've done the right thing. My first mbam scan found several Vundo trojans and a number of PUP and PUM threats, which AVG had not. I deleted all, assuming they were dangerous, but now understand the PUP/PUMs may actually be ok. I think my action has caused problems because my system has slowed dramatically. Changing to Chrome (from IE) seems to have helped, but I don't know why or if I am just imagining it. Not being technical, can anyone offer any advice on how I decide what to delete next time? How do I decide what's safe and what's not, apart from the obvious trojans and virus'? Should I now delete everything in my quarantine? Thanks.