Mod Edit: Split from http://www.bleepingcomputer.com/forums/t/507190/cpu-lag-spikes-when-moving-mouse/ - Hamluis.
I have the exact same issue and (disturbingly enough) have almost the exact same system specs as you.
i5-2500k @ ~3.6ghz
I bought a razer:deathadder to replace my insanely old junk microsoft mouse, I believe that these problems started when I installed the drivers but I cannot be absolutely certain as I didn't notice it for a little while.
I tried uninstalling the razer drivers and I'm currently running the mouse on the default MS mouse drivers (the generic ones that activate when no alternative driver is found) with the exact same issue and, unfortunately enough, even with the drivers uninstalled and a different mouse I appear to have the same issue.
I get the feeling that it is somehow correlated to my gpu though, because the cpu spike is specifically (if and only if) my mouse is hovering over the desktop space. If I cover both my monitors with windows of any process (games, command prompt, explorer windows, etc) then no-matter how many mouse events I create explorer.exe hovers at less than 1% (as it probably always should). This idea is furthered by the fact that on my main monitor which runs at 60hz the cpu spikes to roughly 15%, whereas on my side monitor which runs at some lower maximum hz the cpu spikes to roughly 8%. I find it highly likely that there is some correlation, but it's extremely hard to determine where the problem actually lies, as I think it originated from razer's software but now appears to remain even after the drivers are gone without a trace.
I'd be happy to troubleshoot if someone more knowledgeable about such things is available, I'm more than happy to investigate further as I find this rather intriguing.
Initially I assumed I'd be able to figure it out by creating a dump of explorer.exe through process explorer but that has proved fruitless as I don't know what information to scan for in such a large binary.
edit: sorry to bump a few week old topic though!
Edited by hamluis, 03 October 2013 - 05:13 AM.
PM sent new OP - Hamluis.