There will not be any negative impact whatsoever- it's just like adding any additional hard disk. If anything, using it to move things like the paging file off the OS drive will actually help performance. Another option is to use the second, older SSD for a second OS you might want to try- I actually use two SSD's in all my builds, one for Win7 and one for Lubuntu. That way I can easily alter/remove/reinstall either OS without the headache of dealing with the other. If you're just sticking with Windows though, using it for the page file and your download folder will definitely help with the performance/lifespan of the new 840. Nice choice, btw!