Click Start
Click Run
Enter msconfig
Click OK
Select the Startup Tab
Deselect everything
Reselect any security related applications
Reboot
Download the following free software:
Spybot Search & Destroy (and run it weekly)
Piriform's CCleaner (and use the registry cleaner)
Defragment your disk.
From time to time right click on the taskbar and select Task Manager - it shows what's happening to the machine - what's running and where the effort is going
Do NOT be tempted to mess around with the PREFETCH files - some people will advise you delete them - it's a mistake and solves nothing.
Any slowness now may well be due to the speed of the IP traffic in and out of the machine - acording to an expert I heard yesterday most of the problems in this area are less due to the volume of traffic and more to do with interference - worse in highly populated areas.
Good luck...
Peccavi, October 2009