It is .Net 2.0 that is required (though it is actually only required for the import/export functions), so it looks as if your system does have it installed ok (v2.0.50727).
I also run Outlook 2007 XPSP3, and it loads up for me. Are you on version 1.2.2? I updated it a couple of days ago due to other issues, so it may be worth downloading the latest version. If that still doesn't load up post back and I'll post a version with the .Net check disabled (but with the import/export disabled if .Net not available).
The check is a simple registry key check as recommended by Microsoft:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\policy\v2.0\50727="50727-50727"
if .Net 2.0 is installed.
I can actually change this for a file check, as a file needs to be run to register the .Net helper anyway, so the existence of that file will show that .Net is installed.