First thing is how much memory you got?
Second once it boots go to Start - run and type MSCONFIG.then click the start menu tab and uncheck anything you don'need running in the background.this can cause one to boot slow.
Then go to contol panel - internet options and delete the cookies and history.then go to start - all programs - accessories - system tools and do a disk cleanup and defragment.
Also download this and install update it and run it.
http://dw.com.com/redir?pid=10639408...-10639408.html