Slow boot problems on any computers are due to 2 reasons :
(1) Hardware reasons and
(TRY THE SOLUTION MENTIONED FOR SOFTWARE FIRST, IF THAT DOES NOT HELP, ONLY THEN TRY THE HARDWARE SOLUTION)
HARDWARE REASONS> if your system has less RAM (memory) then it can cause slow boot up issues,
SOLUTION FOR HARDWARE > I recommend you to check the amount of memory on your system., to check the memory on your system , click on start , then "right click" on "my computer " icon and select properties.. on the screen you will the the amount of RAM installed. I recommend 1 GB of RAM on a computer.
SOFTWARE REASONS> These can be a problem with the windows XP operating system.
SOLUTION FOR SOFTWARE> perform the steps as mentioned in the following links :http://www.microsoft.com/atwork/getstarted/speed.mspx
(Click on the above link)
All the best
Have a nice day!