Odd…usually people go with ram that is in matching pairs,especially with dual channel.Did you add any ram or other hardware recently? Is it all the same speed? I’d try running just the gig stick or 2 512’s in dual channel.
Drivers need updating,go to nvidias website and get some new ones.
Do you have anything running in the background that is slowing your system up? Programs,spyware,viruses?