Nothing ever springs to my mind ...
but this lot sort of shuffled between my ears
I'm sure roj and ethel are both on the right lines ... but if not I wonder if it's a lateral thinking thing ... but it could also be something that isn't loading up ....
some timeouts are ridiculously long ... yet won't give an error message (network, virus and adware scanners tend to load just before the desktop).
Kaspersky "scan startup objects" adds about 40 seconds to the startup time of one of my machines
I think if your HDD was on it's last legs you'd have clicky noises ... and other hints - but have you defragged it in the last 10 years??
I like this little app better than msconfig
http://www.mlin.net/StartupCPL.shtml
you can use it to disable startup options but not permanently