It the behavior you are experiencing is a general balkiness, with the mouse movement being erratic, etc., then some badly behaved background application could be consuming most of the CPU resources.
First, defragment your hard drive(s). If this doesn't fix the problem, then quit all background programs using Ctrl-Alt-Del except Systray and Explorer. Open Windows Explorer (from My Computer) and see if it shows the devices quickly under those conditions.
If it works OK with background programs closed, then you need to troubleshoot to find out which application is causing the delay.
The shareware program TaskInfo 2003
is a good resource for monitoring all running applications and drivers (much more information that Ctrl-Alt-Del). It also identifies CPU % utilization by application, so you can easily see if a misbehaving application is consuming all of the resources. If this happens to be the case, you can right click on the application and terminate it.