Probably nothing! I tried to install 4.3 on Vista Biz and 4.3 didn't recognize office '07 [outlook and such] so I gave up.
It's really not that different [other than style / looks], so I just stopped wasting my time...
__________________ Magnum - Themes & More
9000 [Bold] v22.214.171.124 - Current
8300, 8700c, 7100g, 5810 - Laid to rest