This could be any number of issues causing this lag.  I once had an
antivirus program that did a prescan of the computer's hard drive before it
would allow XP to finish booting.  There are some disk management programs
that also scan the drive before starting.  Both of these started their scan
immediately when the Loading Personal.... was showing.

There are a few programs out there that you can run that will show what
programs are running during the logon process.  Can't remember their names
but they have occasionally been referred to on this and other MS newsgroups.
If I find the reference I'll repost otherwise hopefully someone else will
know the name and URL of a program.