Are they all in the same format like mp3 or another readable file type that the Droid can read?
What format are the songs? If any are .wma, they won't play unless you install a music player app that plays those type files.
various formats... is there an app that you would recommend yto play all types?
You could also search for a PC/Mac program that would convert those odd files into the more popular format you have. Power Amp is by far, a very awesome app. The app's price is reasonable, and if you take any of the Google Surveys (a free app that pays a few cents to $1 per 2-3 question survey) you can make enough in a few various surveys to buy it for free.