The Windows 10 April 2018 Update began rolling out on Monday and it came with its fair share of issues. Initial reports revealed problems with microphones, sounds, and mice, as well as system crashes when using Chrome.
To be fair to Microsoft, the team has been working diligently to fix these issues. The browser crashes have been fixed already, and everything else is being worked on. Unfortunately, some users are having problems updating in the first place.
A number of users on the company's support forum have reported error codes. They range from 0xc1900101 to 0xc1900209, 0xc1900209 and 0x80240034. The installer provides no further detail than this, simply reverting the update and requiring the user to download it again.
However, it seems that the majority of these have roots in incompatible drivers or software. Programs like anti-viruses, iso mounters, can cause the error, or anything else that locks or modifies files. Problems can also arise due to incompatible drivers.
Fixing Windows 0xc1900101 Errors
Before anything else, it's worth updating all your drivers and uninstalling any of the above programs. You should visit your hardware or laptop manufacturer's website to grab the correct version for your specific model.
If the error still persists, you may get some relief from Microsoft's Windows Update Troubleshooter. You can download it here or type troubleshoot in the start menu. You may also have to download the latest SSU and KB versions for your current Windows install.
If you have no luck after all this, we encourage you to wait a few weeks. Microsoft will be rolling out the first set of fixes on patch Tuesday, and third parties are gradually catching up with driver support.
In the meantime, you can set your connection to metered in Settings>WiFi to stop Windows download the update automatically. For further help, head to the Microsoft Answers forum.