You could use a virtual audio cable thats available for windows to route it to your sequencer.
http://www.ntonyx.com
But the new GigaSampler 3 will have Rewire and also there is a Vst wrapper for GigaSampler which is in development. due to be released soon.
On the other hand you could go totally for a new soft sampler, perhaps something like kontakt or halion would suit your needs.
