Is my Enermax PSU starting to fail?

I have an Enermax 350W PSU installed in my Athlon XP system that is over 5 years old. Recently, I have been experiencing a problem where I can hear my Windows hard drive click (as though it is spinning up for the first time), the HDD activity light goes solid and stays on and Windows freezing requiring a reset or cutting the power.

I would have thought this is a problem with the hard drive but I have had the same thing happen with two different drives installed idependantly of each other. I have also tried swapping my RAM into different slots but no matter what, the computer can be on for minutes or hours, it will still freeze with the HDD activity light fully lit.

It could be that both of the hard drives are failing as they are old enough to be out of warranty but the chances of both of them failing at the same time with the same problem doesn't seem to be likely.

If it isn't the PSU what else could be the problem?

It can be the PSU if you have eliminated the motherboard and other components. If it is under warranty, RMA the PSU. If it is not, open it up and check for bulging caps on the secondary side.

If you dont have another PSU handy borrow one from friend and see if it makes a difference