Do I have a PSU problem?

[vsrdan]

One of my computers is "acting funny".

Here is the system:

Dual core Intel Presler 945
Gigabyte P45 MB
Five HDs (two of them RAID 1)
One DVD RW drive
4GB RAM (2 x 2GB)
Radeon 800XT (Gigabyte) PCI-Ex card
Card reader
Three case fans
Xclio Greatpower 550W PSU

This system was built in 2006, and was running problem free until now. Here are the problems:

(1) When the computer is turned off (after the PSU fan is turned off) I can hear a humming noise. If I turned off the powerstrip, this noise goes away. I suspect that this could be coming from the PSU (a bad transformer or so).

(2) Sometimes, computer is constantly trying to read the DVD drive, even if there is no disk loaded. This makes an annoying noise.

(3) USB ports are underpowered. The computer cannot read a USB powered external HD (the same HD could be read off a laptop without a problem).

Would changing the PSU solve these problems?

 

[Zero82z]

1) This is coil whine. It's very common, and not harmful. Nothing you need to worry about.
2) Not caused by the PSU.
3) Sounds like a motherboard problem to me.