Mounting a WIM image
From Birnam Designs Wiki
You can mount a WIM image (disk image) with the imagex utility. This is available from the Windows Vista Automated Install Kit (WAIK).
The syntax is:
imagex /mount (read only) /mountrw (read-write) [path to .wim file] [image number within the wim file] [mount path]
So for example:
imagex /mount f:\images\desktopimage.wim 2 c:\mounted(to install wimfltr.sys, right click on the file and select install, then reboot)