Question : Problem: Dell Dimension 4300 powers on without switch

I have a Dell Dimension 4300 that powers itself on even after unplugging it and plugging it back in. It currently has Windows ME as the OS. It has 512 MB RAM (replaced) and I have tried diffferent hard drives to see if any of this affects it. (It also gets an error tryitg to load Windows XP but that is less of a concern right now).This does not occur all times but most times. Is this a motherboard issue? (I thought of power switch but not sure..)...thoughts? comments?

Answer : Problem: Dell Dimension 4300 powers on without switch

This may also be a PSU issue. That is more likely than the mobo being fried.

Can you get your hands on a replacement PSU to test this? The PSU may be leaking power and causing the computer to start up as soon as power is available to the PSU.

Any chance you can try that?