Importing WeightMap onto different skeleton?

Currently I’m working on porting a model, and I’ve applied the valve.biped skeleton to it so I can give it animations and the like. Thing is, the weightmap it came with is naturally made to work with the original skeleton, and any attempts to just import it over the newly rigged model just gives me errors. The two skeletons are mostly similar, although I’m not sure if the heirachy is exactly the same. Is there any way to do this, or will I have to just import a weightmap from a valve.biped model and alter it to fit my needs?
EDIT: Oh, and I’m using XSI Mod Tool 6 for all this, but if I’m required to use another program to do this I’m happy to.

Bumping this, would like some clarification.

Last bump I’m going to bother with on this. If it helps gain any interest, I’m asking so I can port a bunch of Vampire: The Masquerade - Bloodlines models, and I really don’t want to make the weightmaps myself for the models, especially not given how awful some of them will be to weight (trenchcoats, ughhhhh)

from what i know (ive been using softimage for 6 months) is you can’t transfer the weightmap from one skeletonto another. but ive never had that problem before. you can transfer animations (ive done that before, by double clicking on the animations stored in the mixer.)

only thing i can say is do it yourself. tbh its not that hard its just time consuming.

When I’m binding a new mesh to the valve skeleton, I honestly just cut and paste the skin modifier from the original mesh to the new mesh. OF COURSE I have to do some adjustment from there with manually adjusting some vertex weights, but no method other than deliberate work will give perfect results. I do this in 3DS Max.

I didn’t know you could do that, thanks!