I'm basically only thinking of replacing it because I've found that sometimes it won't turn on first time. It always works fine after I've flicked the switch on the back of the PSU off and on again, but as I'm selling this machine I thought it might be an idea to look at a new PSU.
Basically if you turn it off at the mains then when you try to turn the PC on the whole thing doesn't load up, the fans kind of to a half-arsed spin and the GPU lights are red rather than green. Then if you keep it like this (as in don't turn it off) and quickly turn the switch on the back of the PSU from on to off and then back on again instantly then the machines powers up properly and is fine again until it is turned off at the mains.
Because I'm selling it, I don't much care what PSU is in there, just that it works with as little cost to me as possible.
Thanks,
G