A quick search on Newegg turns up numerous cards that fit your bill. Here's one where the reviewer specifically says they're using Win 7. http://www.newegg.com/Product/Product.aspx?Item=N82E16814133233
A second solution would be to use a couple USB to VGA adapters to add monitors.
Finally an expensive, but more stable and future proof, option would be to replace one of your existing PCI-E cards with one that can handle more than two displays. There are many options up to and including ATI's Eyefinity cards which can display 6 monitors with one card.
I bought the video card but it didn't work. I contacted PNY and they confirmed that it wouldn't work.