Find out if Singer has a free download software that you can use. It won't be as complete but it may be a patch until you can afford to update your PSW software. Of find out if an update is affordable.
I can no longer use my Bernina software on one of my computers because it is uncompatible. My son wants to update my old computer from XP to Windows 8 but I said no - not until I can replace my software. Bernina does have a VERY modified free software for download but it doesn't do much. So I hang on to my old computer.
If you can keep your old computer just for your sewing machine - then do it.