i want to know how to upgrade my 512 mb to big
and speed the speed to
Not entirely sure what you're asking, but if you'd like to know more about upgrading your ram, Apple has some nice info over here.
http://docs.info.apple.com/article.html?artnum=58007
You can upgrade the RAM easily
(the type of RAM you will need depends on exactly which iMac you have)
You can upgrade the hard drive with a bit of effort disassembling the machine (probably not good to do if its still under warranty). Easier is adding an external Firewire hard drive.
You cannot upgrade the processor speed.
17" intel iMac can take 3gb of ram.