I couldn't see this little tip anywhere, but after I had this issue, and after much hair pulling, found the solution, I thought I'd better share:
If like me you use an SSD, have your Windows C: on the SSD, but then move the Users directory onto a bigger HDD (eg. D), then you may hit a problem installing Windows 8.
If you followed this: ( http://windows7easy.wordpress.com/20...-installation/ ), or a similar method and used "audit" mode during installation to relocate Users then you'll spot a problem when Windows 8 is installed.
What you'll see is the "Modern" interface but with only a handful (as in 4 or 5) tiles. Clicking the Windows Store does absolutely nothing. You won't get any errors, or even messages, it just won't work. If you delved deeper you'd have seen some License errors in the error log. All very strange.
The secret lies in the alternative way of relocating these folders.
One of the other ways of relocating these is to create a hardlink (or redirect) to the new location. Doing this when the Users folder isn't in use is a bit tricky, but it's easier than typing odd scripts in Audit mode. If you'd done this however you'd not have had a problem. It seems that Windows "Modern" UI -MUST- have A c:\Users folders otherwise it won't work properly. Even a hardlink will suffice, but doing it the audit tool root, won't.
So use this to add that link in:
mklink /J C:\Users D:\Users
And that's it, simple fix.