Peccavi tips are good. Some additional ones:
If ie, any version, is to slow to start, it's often due to to many addons and tool bars.
Try starting ie without addons. Start only those you realy want or absolutey need. Uninstall all the others.
Disable and uninstall the mostly useless and redundent third party toolbars. The toolbars from anti-virus are among the useless ones...
If Windows itself is slow to start, try disabling any preloaders and quick starters. They only make the computer slower to start.
Cleanup your startup folder in the start menu.
Many icons in the notification area are not realy needed. I have full functionality with only 4 icons in addition of the 3 system ones. Set any you don't realy need all the time to NOT start with Windows.
Uninstall any application you no longer use.
Install and run Ccleaner. It's a marvelous cleaning utility. To be used about every 1 to 3 months.
File clutter can bog you down.
For any hard drive, but NOT CCD ones, get some good defragmenter, like Defraggler or some other. Set it to run every week, or set a "smart" schedule if available.
File fragmentation on a hard drive impose a severe performance loss. CCD drives don't need defragmentation as there are no moving parts.