I have three solutions for your reference!!!
1.Pressing enter "FM / A->B key" + "REC key" will rebooting!! Please try again...
2.Reseting power plug
3.Firmware update!!!
Firmware update process (While mega player can't be recognized by PC):
1.Please download and install the latest firmware and driver!!(http://www.msi.com.tw/program/products/ia/ia/pro_ia_detail.php?UID=601)
2.After firmware installing will show some files, please cover driver installing files(C:\Program Files\MSI\MS-5516)
3.Please plug your mega player 516 in your PC and press ?play key? continuously.
4.Please enter OS "start" (below left corner) and enter "programing collecting" and choose to "MSI MS-5516" update now!!!
5.After update success you can release of your hands
Hope to solve your issue!!