You can always give it to the charity as is.
I do charity work and i receive computers, sometimes complete with os, sometimes complete without os, sometimes only partly complete, sometimes i just receive parts, motherboards, cdroms, ram, you name it. I also receive things like win 95 install disk with licence to install on a single computer.
So the charity may very well be able to take care of the win95 on its own. Pretty well all charities have someone who does all their computer work.
Also, you could get on some forums that buy, sell, and trade. You could get one for free if you pointed out it was for a charity.
I just started one myself where you could join and ask for a copy for free, and i know exactly who there would send you one! But i dont know if i can give my forum web address here, they may not allow that.
People like edfair would know if its ok. If not you could email me and i can give you the web address.
So you have a few options.
Good advice + great people = tek-tips