I'm surprised I couldn't find this question trough the search. What's the easiest/best way to mount an ext3 formatted partition in Windows (7 RC, in this case)?
Just found this overview of three ways to access an ext3 partition. Don't know if the first supports Windows 7; the second supports Vista so it likely does. Both of those are just file managers, though.
The third, Ext2 IFS, is the only one I've heard of before, and it does support ext3. It sounds like you wanted the partition mounted so all apps can access it, and that's what this does.
I found various answers for Windows in general with this search. "Four Applications for Accessing Ext3 Partitions From Windows" looks like the most comprehensive look at it - from having spent 30 seconds on each of a few results.
I don't know whether any of them will work with Windows 7, mind you. This guide is for Vista, and I suspect Windows 7 is similar enough to Vista for that to be at least worth trying.