If your system is messed up, I suggest you to do a fresh reinstall of your OS... Or to do a system recovery if you can.
As an alternative, you can convert your old skins (the ones that give you the oldskin.dll error) with BSP SkinMaker (link in my signature).
The only thing you have to do is to load your skin in my program, if the skin is a BSZ skin then press the button EXTRACT in BSP SkinMaker, say OK to the message telling you that the skin is an OLD type skin (and the program will convert your skin), then save the converted skin!
Now BSplayer shouldn't give you any error message regarding skins!
Bye
