how do i convert *dat(VCD) to *asf

You can convert to DivX rather than asf. Use VCDGear or similar to rip DAT file to mpg file on to your HD. Then load into VirtualDUB, set Audio & Video to Full Processing Mode. Set Audio compression to MP3 and what ever bitrate you need. Set Video Compression to DivX and pick a bitrate you also need. Then Save AVI.
 
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