I see you have a couple of other threads about this, out there on other sites on the Internet.
More RAM might help. Go easy on those Registry Cleaners/Optimizers - sometimes they do more harm than good. Check you haven't got too many background services running (Taskmanager, Processes) using up CPU and ram memory. Check the size of the Virtual Memory allowance. Also is your Virus Checker running a full file scan at every boot up? That can slow everything down and there is no need for a full scan to run at every boot up. Change the schedule.