Slower-than-normal XP startup

For a little over 2 months now, my computer has taken a little longer to load up. It sits on the XP Home Edition screen for about a minute or so - definitely not a huge problem, but considering it used to sit there for 30 seconds or so, it's a noticable wait.

When XP loads up, it seems that applications are a little slow to startup on their first try. The opening sound seems to stutter a bit, and programs from Media Player to IE to other stuff (FTP prog, my HTML maker program) are slow on the uptake. But if I shut it down and open it again, it opens right up; no problems. Occassionally, the cursor is a little sluggish - it's move normally and then seem to skip a bit, but it comes and goes for brief amounts of time.

Also, Norton Anti-Virus (also slow to open) takes a LOT longer to scan; a little over an hour, versus the usual 35-40 minutes.

I've tried everything to clean up my computer. I run Spybot and Adaware more often now, I've gotten rid of a bunch of unneeded programs that came with the computer, I keep up with Windows updates (haven't touched SP2 yet but this started before that was offered anyway), I *always* clear out my temp. internet files and I regularly wipe out old stuff in my TEMP folder. My RAM and disk space are not being overly strained either.

And when I shut down.......no problem. As quick as ever.

Again, it doesn't seem to be a big problem, but it's an annoyance I've come to live with......but wouldn't mind to see go away either. Any ideas?