Unable to install 4.2 PTR

[halmotors]

Okay, so I'm trying to install the 4.2 PTR, but when I try to use the installer it gives me this error message:

The installer does not need to be applied. It requires a version of "Wow.exe" older than 4.0.0.12635, but you already have version 4.1.0.13682.

I don't have a PTR folder in my World of Warcraft folder, nor can I find any way to log into the PTR from my regular game client. What exactly can I do to fix this? I've tried doing a search, but I couldn't turn up anything that helped.

[halmotors]

Bump. Still would like to figure this out so I can hop on the PTR.

[Archimand]

make a folder called World of Warcraft Public Test case sensitive then try to run the installer again
make sure that when the launcher ask you where to install it you do it in the same place as that folder

if it say The installer does not need to be applied. It requires a version of "Wow.exe" older than 4.0.0.12635, but you already have version 4.1.0.13682.
you either trying to install it inside your retail folder or already have a ptr installed
once you done it will do thing called run once which will copy your entire wow folder to the ptr just let it finish then you can start patching

[halmotors]

Ahh, I didn't realize you couldn't install it to the retail folder, I could have sworn you used to be able to do that. I'll try your advice right now and see how it works.