Installing Windows Media Player 9 is NOT a big mistake. Far from it. It's a good idea, because it is a much improved player.
As for playing SVCD's, WMP does play it OK, but it does not support menues and chapters. For this you better use a player like WinDVD.
If both WMP and BSPlayer cannot play your SVCD, maybe you don't have MPEG2 codecs in your system. Download and install the Elecard MPEG2 Video Decoder:
http://www.elecard.com/download/