You did good. Thank you.
1 gig of ram is minimum but that is not the problem. Game Booster from
www.iobit.bit can disable some services and programs eating into your memory.
Your graphics drivers are two years old. If AMD/ATI has new ones, it would help.
ati stopped producing good drivers for AGP's
Have you updated your .Net framework to 3.5 SP1? Do it manually. if you have not.
Yes
Have you updated Windows media Player? Same thing.
Yes(at least this is what i read in unistall applications)
If that does not solve some, then you have other conflicts.
Good luck.