Not really advisable to load DX9 for this card as it doesnt use any of the new DX9 functions. Its at the moment for the newer Radeon cards People have had problems with it. But to answer your other part of the question click here
Depends - I have the GeForce 3 Ti 200 and the new Detonator 42.01 Drivers (which are DirectX 9 Compatible). Whilst the card may not support all the DirectX functions it hasn't done any harm. In fact the card has picked up a bit with the DX 9 and the new Drivers.
I use a program called GoBack to make sure I can roll back to before the drivers where installed (DirectX is very difficult to uninstall if at all) A 30 day trial of this program can be had from click here
Theres no reason to not install it. Applications will start to require it in the future. A lot of people are still using graphics cards that arent fully DX 8 compliable but they work fine. Give it a go. I have and its fine on my GF3 TI 200
This thread is now locked and can not be replied to.