According to the user manual for the MA933ASC, if you're not using Windows 98, the player should be recognized as a removable drive if you plug it into the USB port on your computer.
To erase your songs, connect the player. Open "My Computer", and find it listed as something such as "Generic Removable Disk", maybe drive G:\ or so seems to be popular in Windows. Once you're browsing the files on the player, you can delete them as you would any other file on your computer.
Hope this helps, for more information you can find the manual for your player online
here.