When she shuts down the PC and then starts it again (not a restart), explorer.exe does a few seconds of house keeping and releases the CPU. On the second start, the Task Manager shows memory reserved for explorer.exe as 27,700K but the CPU is sitting idle 99% of the time.
Any ideas

System specs:
Dell Dimension 4600
1.25 GB Dual Channel DDR SDRAM @ 400mhz
Windows XP Home Edition (up to date)
MS Office Pro
Norton Internet Security with NAV (both are up to date)
Spybot