Goto Start, Run, and type
msconfig
Goto the Startup tab, and look for anything in there that you don't need when booting (Don't untick anything located in WINDOWS\system)
I have hundreds unticked now, as everytime you install a new software it appears to run on startup (in the background) which slows everything down including IE.
Things like MSN, HP Printer software, Google Update, Adobe etc etc.
Press Apply, Ok, and reboot.
You should see a difference straight away, once loaded, a pop up will show, tick the box and ok.
Let us know your findings