Firefox Portable > Tools > Options > Advanced > System Defaults > Check Now
set Windows 2000 > Tools > Folder Options... > File Types > HTM (and others) > open
to "C:\FirefoxPortable\App\firefox\firefox.exe" -requestPending -osint -url "%1"
Why not
to "C:\FirefoxPortable\FirefoxPortable.exe" -requestPending -osint -url "%1" ?