Can Unreal access windows registry?
Sure why not? Include Winreg.h and call RegQueryValueEx. There isn't anything in the engine to allow a platform-generic way of doing this since the Windows registry is Windows platform-specific, so you won't find it in Blueprints. If you however wanted to expose a function to your blueprints that did this you could do so; the following code would give you the ability to call "ReadRegistryValue" anywhere from a blueprint.
if you're stuck on
try adding this include: #include "WindowsHWrapper.h" :)
edit: i found some typos, below a snippet that will compile:
Follow this question
Once you sign in you will be able to subscribe for any updates here