If you purchased the 1881 Census from the LDS and I have now upgraded to Windows 7 you won't be able to  access the information. 

The LDS says they no longer support the Reader and that whilst you can work around it to get 7 to emulate XP this won't work for Windows 7 Home or Home Premium. 

Apparently to get over this problem it's possible to install XP emulation mode: http://www.youtube.com/watch?v=CbEK0jD6GlE