Also consider it could be the network card drivers. Brian Weeden wrote:
A while back I was running into a similar issue with svchost taking up a lot of CPU resources and it turned out to be a bug in windows update (a race condition I think).From what I can gather, svchost is involved in a lot of network stackoperations so you might want to use a tool like Wireshark to see if the CPU spike corresponds to network activity.
