I've had this computer with Windows 7 for about two weeks. Within the past two days, the shutdown process has become extremely slow. Only changes have been updates. Startup time seems about normal. Dell 580 Inspiron with 6gb memory.
The cause could also be a USB device, I had a External drive that started to act up and shutdown and start-up took forever. I disconnected all USB devices and then connected each one individually did a shutdown one by one until culprit was found it I found on the second try I got lucky. It was a Maxtor 350 Gig drive that went T#ts Up