As the biggest of the problems seem to be associated with Spyware, for starters, download, update and run a full scan using the following product:
http://www.superantispyware.com/
SuperAntiSpyware is exceptional and will remove the majority of difficult Trojans and Worms, not just the easy ones.
go to your start menue and selct run...type in msconfig then select start up tab
A wndow will pop up showing you all the needless programs comeing up every time you turn your computer on.
Start unchecking those needless programs that are slowing you down then click ok, You will need to reboot for the changes to take effect.
Allso defrg often,do your disk clean ups weekly.
Cleaning your registry will allso help you speed your computer up.