There is a process,
wmpnetwk.exe, which sometimes goes crazy and starts eating like 60-70% CPU. If I kill the process it just comes back again, so the only solution I've found is to stop the
WMPNetworkSvc service, which makes the whole thing stop. I think the service comes back again too after while, but I think that's because I turned off the computer.
Anyway, I don't use WMP, so I don't care if this is disabled, but I'd like to know what's causing it (Google has revealed that it also happened to other people), and if there's a more permanent way of fixing the problem.