Slow start up can also be due to the number of programmes and utilities which automatically come on at boottime. Most of them don't need to and will still work perfectly well when you call for them but you can prevent them starting.
Either go Start>Run or use your Windows key and R to bring up the Open box and in it, type msconfig and press Enter. Click the StartUp tab and untick everything except your firewall and anti-virus. Click Apply and then on the Services tab. Tick to "Hide all Microsoft" and look carefully at the remainder. Many can be stopped but post back if you have any doubts.
Click Apply and Ok your way out and after the restarft, tick the "Don't show this message again" box and press Enter. Your next restart after that one will be significantly quicker. XP can boot in 35 seconds.