I have an ASUS Radeon HD6570 1GB DDR3, well under $100.00 works like a charm.
I have the GT240 Nvidia card and have seen the same spikes with Latencymon. I have researched this in the past and have never been able to find a solution. I have tried multiple Nvidia drivers with no success. If you find a solution for the Nvidia card let me know. I purchased an AMD Radeon HD5450 card that does not cause the spikes. The card is not as good as the Nvidia however. Good Luck !
Sorry you have problems.
Do you have AERO on or have you disable it so it look like Windows 95? If you have disable it, then that’s your problem.
AERO need to be on to make your programs and system work correctly!
Also many user get fooled into or they just continue to apply old tweaks, “XP tweaks” that was good on XP only.
On Windows 7 & Windows 8 system they are not valid tweaks. Instead old XP tweaks are instead counterproductive tweaks on those new system and should never been applied in the first place. That also cause a lot of problems too.
Hope it helps you figure out what is the problem in your setup!