Check the Event Viewer. Goto Start > Run, type in eventvwr.msc, (for clarity that is EVENTVWR.MSC), and click OK.
In the new window, start investigating the entries under both System and Application. What you are looking for is the 'time' entries, in other words, the time delay between entries. If you see anything that looks like a time delay of 2 to 2.5 minutes, then you have found your culprit, probably the entry below it.
I would hesitate to start doing anything in the registry, A wrong move there can kill an OS dead.
I have a specific delay in my XP bootup. All goes quickly until the wallpaper display - then there is a wait of 2.5 minutes before the desktop icons appear. I suspect the delay may be one of the services - but I have not been able to figure out which is causing the delay. What could be running in that specific interval?
I tried the stndard things - disabling various servicdes and startups. leaning registry, etc. Is there any way I can find out what is runnin duing that period? By the way, hard disk activity is minimal during the delay.