Check what programs are starting automatically in your startup folder.
You don't need your satnav, mp3, office software running all the time - it slows down start up time and hogs resources.
Start - run - msconfig
Click the start up folder tab
If you see anything there and you are positive what it is, and your computer doesn't need it to run, untick it.
If you are unsure as to what you are doing, download Startup Inspector (free)
http://www.windowsstartup.com/
When the program is running, click 'consult' and deselect all the unnecessary stuff