Shutdown Works But Is Very Slow
If it appears that Win XP is not shutting down, give it some time. Some users report a minute or longer for shutdown to visibly start. Generally, this is a consequence of software that is running when shutdown is attempted; it also may have something to do with particular hardware. If you experience this problem, be sure to close all running programs before attempting shutdown and see if this solves your problem. If so, then you can determine, by trial and error, which program(s) are involved.
One specific solution for this. In Control Panel | Administrative Tools | Services, stop the Nvidia Driver Helper service. (You can also get this by launching SERVICES.MSC from a Run box.) Many other newsgroup participants quickly confirmed that this solved this extremely slow shutdown problem for them.
Another possible solution: In Win XP Professional, the Group Policy Editor has a security option to clear the pagefile at system shutdown. The same setting also forces the hibernation file to be wiped at shutdown. These processes take long enough that users may think that shutdown has hung. Since someone actually has to have set this policy, the problem will be pretty rare, but is worth mentioning. To change the setting, click Start | Run, type GPEDIT.MSC, click OK. Drill down to Computer Configuration | Windows Settings | Security Settings | Local Policies | Security Options. In the right pane, find Shutdown: Clear virtual memory pagefile.