i use these tips every few months to speedup my pc .
my laptop is a 4 year old acer aspire that runs windows xp and a lot of free opensource software.
most of the clean up steps and apps will also work in windows vista and windows 7
Step 1: Speeding up windows part 1
goto start > all programs > accessories > system tools > disk cleanup
select the c:\ drive > select al catagory's and press ok.
this wil free up system space and will make you laptop run faster ,because windows will not have to keep track of all those unneeded files
Step 2: Speeding up windows part 2
this is for the people that dont use my recent documents .
my recent documents is a feature of windows that loads the most recently used files in to memory for if its needed later and if these files are large files the will take a lot of memory.
slowing down your pc . because i dont use this feature a lot i will show you how to clean the list and disable it .
go to the startbar and right-click on a empty place of it > go to click properties > click on the button "start menu" on the top > click on "customize" > click on "advance" on the top > click on "clear list " > uncheck "list my most recently opened documents" > "ok" then "ok"