I was using XP tonight and got really fed up with how long it was taking when right clicking on a folder for the menu to pop up. After a quick Google search for xp right click slow I found an article called "Right-click is slow or weird behavior caused by context menu handlers" which suggested using ShellExView to remove "context menu handlers".
It took just a few minutes to find that it was PGP that was the problem. Once I disabled PGP's menu, XP's right click menu popped up instantaneously. The next step was to uninstall PGP altogether.
After I re-enabled the other "context menu handlers" there was a slight pause before the menu appeared suggesting other slow handlers. I might disable some more later but that was enough tonight.
If you right click on a folder in XP and the menu is slow, you gotta fix it.