Finally, there's a fix!!

Actually it's been out for a couple months I guess. You need to update your Windows Update Agent, mine was from 2014. I'm dealing with a computer that needs 250+ updates. I takes 12 hours to compute all the updates.

After installing KB3020369 (which is needed and I didn't have it) and KB3172605 (Windows Update July 2016) the update check only took 1 minute.

So hopefully after July people got the update automatically and the problem shouldn't happen anymore.

And don't forget ENABLE ALL CORES! That one always fixes all kinds of things.

But I think you're seeing 25% usage because you have 4 cores, so it's pegging one core leaving you with 75% free. The type of systems I'm dealing with are usually dual cores, so I see 50% usage most of the time. Either way it's using 100% of something..

I've tried the KB3145739 fix, KB3083710, and KB3102810 fixes, none fix it. Even tried the KB3145739 fix for Vista, but of course no difference. I've tried deleting SoftwareDistribution all together, but that just made it take even longer to rebuild the whole thing.

Well, I only have about 4 or so years of this crap left until Windows 7 dies and then I'll recommend not reinstalling it anymore. But then there's another 3 more years remaining of Windows H8 crap. Can't win.

You want some real fun, try updating Windows 7 on a Celeron! Argh! Talk about watching the photons grow. Celerons aren't made to do much of anything, let alone mining for Ethereum.

My work computer hasn't disappointed me yet, and windows update is on. It's got a Core i5 3.5GHz w/Win 7. It's always up to date, so I never get much lag when it has to install 5 to 15 updates. Now my home computer has updates turned off. So when I do the chunk of updates I'm sure I'll use some extra electrons from the wall. The price to pay for an uninterrupted and windows update bug free system.

Yup. I've been seeing this since around the beginning of this year. I work in a computer shop and have to deal with this all the time. Customers are complaining that their computer is running slow. We check it, and sure enough it's the svchost->wuauserv process that's eating up 100% of one core. I've seen one of the folders in SoftwareDistribution that grows larger and larger as the CPU usage carries on.

This happens with Vista too. I've had to reinstall 1 or 2 Vistas in the last 6 months and ran into this. It heavily depends on the CPU speed of course. One system I let along for 5 hours straight and it wasn't finished yet. I usually just let it sit over night and finish it up the next day too. This seems to happen more often if you have multiple windows updates pending, or if it's been awhile since you last checked for updates. If you have 30 to 50, forget about it. If you install a new OS with 200+ updates pending, you're looking at a day or two of CPU usage. Eventually this stops and it shows the updates to install. You install them and reboot, and it gets better and better the closer you get to 0 updates remaining.

Not sure if this was something intentional on Microsoft's part, or if they did do it on purpose to steer people into upgrading to Win 10 as they complain about a slow PC. For the most part I haven't seen this issue on Windows 10, since usually the 10 machines I deal with already have all the current updates since that's all automatic now. So maybe a big change they did to handle updates was geared towards 10. It's hard for me to say if this affects any Windows 8 machines, as I have been suggesting and installing Windows 10 upgrades from 8 anyway. We'll see how it goes when the free 10 upgrade is over and are forced to deal with Win 8 machines.

I've been joking that maybe Microsoft is mining for bitcoins in the background and using Windows Update as a cover.