Recently I have been having a slow XP startup that after many sleepless nights I have narrowed down to Kaspersky Internet Security 2010. I believe I have a solution that you may try if you are having the same problem.
Just disable it from running at system startup. Settings/Protection in the application menu. After you have done this go into the task scheduler. Control Panel/Performance and Maintenance/Task Scheduler. It should be near the bottom.
I have scheduled Kaspersky as a task to run everytime I logon and after 4 successive boots, I am having no slow startup. I admit it's not running at computer startup, but if it impedes my use of the computer then it's not really worth it IMO. You might try to run the task at system startup, but I haven't tested it. I haven't really tested this either, but it seems hopeful. Hope this may help anyone with the same problem. I couldn't find any answers.