Have you loaded a legacy bit of Software? The Compatibility Assistant runs either manually or when it detects legacy software that does not conform to the Windows NT 6.x Kernel Security Model. Task Host is usually a background maintenance task.
I've not installed anything new for a couple of weeks now. Yesterday was a weird one though, my Surface went back to doing that annoying thing of going to sleep every few minutes when it's not in use... of course the first thing I did was to double check the power settings, which are set to keep the Surface running for at least 30 minutes. Anyway, at the end of the night, I turned it off and for the first time it didn't show the above message. I put it back on again this morning to check and it seemed to be staying on. It really does have a mind of it's own sometimes!