The software for these machines is not available for public downloading. The software either comes with the machine or needs to be purchased from their official website. You can try to apply a compatibility tweak on your software to install it at least and then apply the available updates downloaded from the following website: http://futura-support.com/products/ce-350/software
If this solution doesn't work, a new CD needs to be purchased. I see their software is compatible with Windows 7.
Here is the official website: http://www.singerco.com/accessories/software