WinPE 2.0 File Associations?

[have_quick]

I'm having a problem getting file associations to work under WinPE 2.0. I've got the MS Word document reader working however I cannot associate .doc files to it, I've tried loading the hives and entering the registry information (OpenWithList, etc.) however WinPE seems to ignore this. I've checked that my registry entries are there so I'm a bit stumped. Does anyone know how this works?