MoBo Might be dieing any thoughts?

[UMfanatic]

I am running a GB K8N Pro in my mom's pc. She doesnt use it for anything other than photo editing, browsing the web, and ms word (so I have not put more modern parts in it.) Well for the last year when you power down the PC the power supply will flicker once the computer has shut off. The fans spins causing the case fans to turn on and the LED lights whitin the PSU flicker on and off. I am not sure if this is a problem with the PSU or the MoBo or both? Can anyone advise?

Specs are as follows

AMD 64 3200+
GB K8N Pro
1GB Ram
ATI Radeon X1300 Pro AGP
160GB HDD
DVDR+/RW
CD Burner