Microsoft has hit on another way to make everybody switch to Win10 - a fresh install of Win7 (sp1!) can no longer download updates from Windows Update, at least out of the box (literally zero software installed or other configuration changes). It will hang saying "Checking for updates". The very first thing it downloads an update to Windows Update, but then for some reason it cannot install that update, gives up, and goes on to checking for more updates, forever (I've tried letting it sit for 3+ hours, no change!). In total I wasted about 3 days of sporadic effort on this problem, reinstalling Win7 at least 5 times onto a wiped disk, before I hit upon this exact set of steps. I ran tons of MS Fixit apps, tried deleting the SoftwareDistribution folder, etc. No joy. What a huge waste of time and effort, almost makes me wish I had decided to go with Win10 after all.
Enough ranting! Here's what works. Install the following files, in the following order:
You can find all of these on microsoft's website (just google them!). Sorry for not providing their actual names, or what they do, but the M$ pages you download them from will explain (to the extent that MS ever tells you what's going on under the hood).
Now launch windows update for the first time. It will take a while (maybe 15 minutes) before it progresses beyond "Checking for updates". Just to be safe, I've also taken to only installing 10 updates or so at a time.