this is a common problem when using wireless equipment in windows. Especially on Dell notebooks. The PCMService.exe program starts when the computer starts and interaction at some level between this and the Wireless reciever prevents the computer from becoming idle. Therefore, the screen saver and the other idle-related features do not start. this issue may also occur if the PCM and DVDLauncher services are running in the background. This issue also occurs in Windows Vista premium and in Windows Vista Ultimate because of the media center functionality that is built in.
Microsoft reccommends plugging in your wireless device and visiting http://windowsupdate.microsoft.com/
to get the "optional hardware update" named "Microsoft HID Non-User Input Data Filter." This should fix the problem.
Microsoft also reccommends two possible "workarounds" for this problem if you do not want to install the update or if the update does not work, both are relatively simple:
1- turn off the PCMService.exe program. to do this, first you open the system configuration (start->run->msconfig.exe). on the startup dab of the configuration window, click to clear the PCMService startup item check box. Apply, Close, and if/when prompted, restart your computer.
2- Remove the PowerDVD Software (not advised if you use this software for watching DVD's on your notebook). To do this, open the add or remove programs window (start->run->appwiz.cpl), locate PowerDVD, click change/remove, and follow the steps through for removal of the program.