I have noticed on some XP machines that the computers are very slow to startup or very slow at normal operations. Some computers take 5-7 minutes to get to the Windows domain login and then 8-10 minutes to login before loading is completed and the system is usable. Looking at the task lists does not really show any big CPU hogs.
I have tried uninstalling not needed items. I have done Symantec Endpoint Protection scans, hitman pro and malwarebytes scans. I have tried tools like Iolo System mechanic, PCTools Registry mechanic/system performance tools, Advanquest Fix-It utilities, doublemyspeed.com tools, and while they appear to compact the registry, find registry mismatches, etc., they do not appear to do much.
I have found some items as the ipodservice loaded with itunes or another peer-to-peer service that no one knew where it came from to have some affect on speed.
What is the best tool to use or what is the best way to identify the cause. I have a different computer that has done significantly more different things without ever experiencing this type of slow downs.