Help: sluggish mouse pointer? (Windows)

[Context: Windows 7]

Garh; this is driving my crazy. For the past couple of weeks, the mouse on my desktop machine has been notably sluggish -- the pointer is "stuttering" a lot, not keeping up with me as I move the mouse. I've replaced the mouse's batteries (a common recommendation), and that doesn't seem to do it. Antivirus is up to date, and I believe the problem is happening a *little* even at system start, although it tends to take a while to become grotesquely annoying; none of my usual foreground processes seem to be involved. Likely related, I'm sometimes seeing difficulty with typing -- stuff I type takes a long time to register, and sometimes doesn't work at all. CPU is *not* pegging at all: moving the mouse around a lot barely registers on the CPU meter, even when it's stuttering and catching constantly.

The problem almost has to be something to do with interrupts and a bollixed driver, but I have no idea where to look to diagnose it. Any pointers on how to track down the offending process, short of wiping and reinstalling the whole bloody computer, would be greatly appreciated. (Comments recommending that I change operating systems would not. Please don't; I'm not in the mood.)

Thanks...

Mixed feelings

Part of my brain is going, "Wow, this is wonderfully beautiful weather!" And part is going, "Wow, this is *disturbingly* beautiful weather!"

Yes, there's the El Nino effect, and after last February I can't entirely look the gift horse in the mouth. But there's something pretty broken about hitting the mid-60s on February 1...