If you turn of system restore you will loose all your restore points. Another restore point will be created as soon as you turn it back on again. I believe they delete as soon as you turn system restore off but i reboot in to safe mode to do my scans anyway.
I like to keep system restore on but reduce the memory usage to the minimum amount. It has come in very usefull when i have installed software and my system has gone pear shaped!
Do not turn off your AV at all

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