HDDs at 100% at idle - Windows Vista

Very often I find Vista using my HDDs at 100%. Currently it is doing it and it is writing at 60mbps. Indexing is off. It's not defragmenting either. Anything else it could be?

Okay I rushed to ask this on the forum and obviously I answered my own question.
It was system restore. Enabled by default in Vista and it does scheduled restore points. I disabled it and now everything is quiet...raid5 wtf

The Windows search service will chew on the hard drive occasionally also.