I've had this before with CPU-Z but with a Athlon XP 1700+ DLT3C it thought it was doing 4.5GHz closed it down and reopened and it re-read correct speed. That version of CPU-Z was buggy wasn't it?
Yeah, that's it - this was quite a while ago, I was just going through one of my overclocking folders and found it. I remember that it kept spiking up to them speeds and coming back down again, so I took a screenshot of it when it was up there
I didn't realise it was a common thing , I thought it'd surprise a few people