Hi taj133,
"I bought the G4 (dome with floating panel) in 2000"
Is this the type of machine you are referring to:
If so, those machines were actually released in 2002. The last one was a 1.25Ghz model. The first, a 700Ghz model, came with 10.1.2 + 9.2 pre-installed and can be upgraded to 10.4.11. The last model of the flat panel from 2003, the 1.25Ghz, came with 10.3.1 pre-installed and the maximum it can be upgraded to is 10.5.8 Leopard.
If browsing and especially iTunes is of major concern then I would recommend at least upgrading the machine to 10.4.11 which will allow you to use later versions of both browsers and iTunes versions. Purchasing a copy of a full retail Tiger 10.4 install dvds can be expensive from third party resellers such as on ebay etc. A good indicator can be found by searching ebay for completed auctions after searching for "10.4 full retail install"
hope that clarifies some,
LS 🙂