what OS are you running? getting above 1gb wont hurt most things anyway. Check for all the background apps running, printer cr*p, digital camera cr*p, mobile phone cr*p basically anything that told you the world would end if you didn’t install the cd first has probably put loads of little background stuff on your PC that waits for something to happen. Check the contents of the system tray (bottom right next to the clock) all you really need is networking and the time.
Also what Anti Virus are you running some slow down incoming traffic to do slower checks. Norton is about the worst from memory