Set your backdrop up on the north side. that way you'll get morning light in the East window, and you can put the backdrop up for some blown out light from the north windows if you want.
time to go yard-sale-ing.... find a shower curtain rod for a backdrop holder, a couple of screw in hooks from the ceiling and some cut and bent wire hanger will secure it. $30 worth of white muslin from walmart. a bag of assorted plastic pony clamps for $8 (useful for holding that reflector you have.. and while you're at it, get this reflector: http://www.amazon.com …TF8&qid=1308246802&sr=1-1
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Single 160ws strobe on the backdrop (enough to blow out the area around people in the picture, and then another strobe (speedlight if you've got it) into an umbrella as a key. You've got the reflector for fill. DIY white seamless, done.
Everything you've read above, I've done, and it worked great. You get 3/4 shots at most for white seamless, can't make the people float without some extra gear (more strobes for backdrop, some tileboard for the floor (which incidentally is pretty cheap)).
Get Cactus v5 tranceivers. $60 for a pair of them and you can add more as you add more lights.