Windows explorer slows down during startup, how to trouble shoot?

Question

Lenovo laptop running Windows 7 Home Premium.

My windows explorer runs VERY slowly. e.g. a RMB on anything in the right hand pane or on the desktop takes 10 seconds, even selecting objects (files or folders) takes 10 seconds.

However, selecting folders in the left pane of the explorer (the tree) or in the top (where the "url" would be) has instantaneous response.

This is with respect to files local to my hard drive, the CPU utilization is low to zero (though the explorer process jumps up to 25% utilization during the selection - on a 4 CPU system).

Interacting with icons in the taskbar is also slow (10 seconds per operation).

When I rebooted this morning, I caught the taskbar while the log in process was still happening, and it responded immediately, I opened an explorer - no delay in interacting. Then all of a sudden the 10 second lag happened again. So it appears that something I've installed and have running is causing this.

What is a good way to track this down? Other than re-imaging my computer, or just blindly uninstalling everything one-by-one?

My startup folder has only one item in it (Dropbox), so there must be some other place where other programs are launched.

Edited to add: The problem in this case happened to be MS Office's Grooveex.dll, which was disabled by configuring MS Office 2010 and disabling the sharepoint (I think, I disabled a few things).

This answer from the duplicated question really helped, specifically the autoruns - which let me look at what specific things were autorun that specifically affected Explorer. That was perfect.