Multimedia player no longer functions after wrong power adapter plugged in - what can I do to resolve this?

Remove the battery and replace it, test. If this does not work, attempt to power on with the AC adapter plugged in and no battery in the system. If this works, you have a bad battery. If this does not work, watch the light on the ac adapter. If the green light goes out when you press the power button, something more is wrong with the system. Further information is desired. When you press the power button, do any lights on the system light up? Do the fans in the computer turn on? Does it make ANY noise? Finally, if available, it is desirable to try a different and known functional AC adapter.

please check your usb port using another device

best way is to just try out the battery on another laptop, or try another battery on yours. If the laptop is not very old, and I suppose yours isn't more than 2 years old, your battery shouldn't be dead.

I have seen no rechargeable device that requires the power switch that lets the device function turned on. Often, it is mentioned that the length of time for a full charge will be longer if the unit is in use at the time since the unit and recharging function both require power and if the player is in use, it logically has priority over the recharging function. In other words, it should charge more quickly if the player is turned off.
Unfortunately, Initial's website: http://initialdvd.com/ is no longer in operation so finding the manual could be a problem. Initial Technology has sold a number of 'turkeys' in the US (we own an Ilo TV) and I think they no longer exist.

You can get power adapters on EBay... just saw them.

the power supply is bad and needs to be replaced. unfortunately, infocus no longer makes them. sorry.

I would change the battey, if its not the battery i would place the media player on top
of some paper, stand back and admire your new paper weight.

Is the adapter the correct one, maybe wrong voltage (5.0) or wrong phasing (ring is -, tip is +)

Sounds like the laptop used up all the battery power and turned itself off. Its doing this possible because your AC Adapter is not functioning correctly. Most AC Adapters have an indicator light to show wether they are working or not. Does your have this and is it on? If the device is still under warranty, contact the manufacturer for a replacement. http://www.msicomputer.com/support/sup_NBService.asp If the device is no longer under warrany, then I would recommend getting a new AC adapter. Make sure you get the same model AC adapter that originally came with the laptop. This will ensure that you have the correct voltage and amperage.