I tried daemon tools and also failed mounting the ext2/3 image. Doing a little more research, I found something that DID work for me.

FileDisk (Scroll to the bottom of the page).

Basically, this is a little utility that lets you mount a image file as a new drive (e.g. "G:"). You still need to install the Ext2 IFS support since filedisk doesn't install any file system drivers.

Read the install instructions for filedisk carefully. You have to (1) copy a file to the Windows "drivers" folder, (2) add some entries to the registry, and (3) reboot. Then you use the examples to mount a image file as a new drive letter. This worked for me for a ext3 image I created in Fedora. And I was even able to write files to the newly mounted image.

If this doesn't work for you, let me know and maybe you can give specifics of the "loopback file" you are trying to mount.