Umax provides no support for Umax Astra 5600 scanner any more. Its drivers are also not available for Windows Vista, 7, and 8. However here is a workaround, download Windows 2000 drivers of this product from the Internet and try to install them in compatibility mode. To accomplish this task follow the steps given below.
•Right-click the printer setup file and click Properties. (If you have installation CD or DVD, copy contents of the CD to your local hard drive.)
•On the opened properties box, go to Compatibility tab.
•Under Compatibility mode section, check Run this program in compatibility mode for checkbox.
•From the enabled drop-down list of available operating systems, select Windows 2000 or Windows XP and click OK.
•Once done, try to install the application and then restart the computer.
I am not sure if it would work this way but you can still give it a try.
Let me know if this helps.