I've downloaded multiple installers for Krita. (I'm using Windows 10 professional.) I've tried the executable installer, and I keep getting an NSIS error that reads "Installer integrity check has failed. Common causes include incomplete download and damaged media. Contact the installer's author to obtain a new copy." The error window then follows with a link nsis.sf.net/NSIS_Error

I have visited the link and it explained the NSIS error as "The installer has failed a self-check. This means that for some actions, the installer file has been altered from its original form. If the install were to continue, the software install would not be complete and will be broken. To prevent further problems, the installer refused to continue." It offered multiple potential fixes, none of them have worked for me.

After getting the same error with multiple versions of the Krita installer, I attempted to use the zip version of it. I couldn't get that to work either, because with every version that I tried, a different file would not extract properly, even if I tried to extract it by itself. There was one version that I did almost get to work via the zip version, but when I opened it, it gave me a popup window that read something to the effect of "Krita does not have any brush presets, the program will now close."

I'm completely at a loss. Here's my specs if it matters:
Ryzen 3 2200G
8GB RAM
RX 580q

I've just downloaded the 64-bit .zip packages for 4.2.7.1 and for the latest 4.3.0-prealpha versions and they both extract with no problems and both run with no problems. I also downloaded the 64-bit installer .exe for 4.2.7.1 and that installed fine; on Windows 10.
Do .zip packages for other applications extract/unpack with no problems?

Do you have any anti-virus or other security software (apart from Windows Defender) running on your system? If so it may be a good idea to try disabling it before you unzip and run to see if that helps.