During a new Windows 7 SP1 installation, it went stuck on checking for updates. I did see Windows update issues a lot last years on Windows 7 SP1. This one is really nasty, because it stays on "Checking for updates" for hours.. Not that cool if you ask me.
The solution is really easy. Just download KB3102810 (Installing and searching for updates is slow and high CPU usage occurs in Windows 7) here and install it on the client. Better stop the Windows Update service first, to speed up the installation process.
Another solution is to download both KB3138612 (Windows Update Client for Windows 7: March 2016) and KB947821 (System Update Readiness Tool) and install them on the client. Better stop the Windows Update service again as mentioned before.
When still having issues, you can try Microsoft Easy Fix also! Hope it helps for you too :)
In the meanwhile the following solution is available too:
Simplifying updates for Windows 7 and 8.1
It mentions: We’re happy to announce that we’re making available a new convenience rollup for Windows 7 SP1 that will help. This convenience rollup package, available to download from HERE, contains all the security and non-security fixes released since the release of Windows 7 SP1 that are suitable for general distribution, up through April 2016. Install this one update, and then you only need new updates released after April 2016.
Other blogposts on Windows update:
Some clients not updating, reporting 8007000E error
Software Update Error 0x80004005 on client systems