I found the answer for my 4830T. This made my SD Card Reader work finally after installing Windows 8.
Go into 'Computer Management' then 'Disk Management' and the Card Reader shows up there. (Go to Control Panel >System and Security >Administrative Tools > Click on the name "Administrative Tools" Then click on >Computer Management Then in the left panel under storage click >Disk Management
Your SD card reader should show up there. Right Click on it and from the pop-up menu choose 'Change Drive Letter and Paths...' or 'Add Drive Letter..' Assign it a drive letter, and viola it shows up when you double click the computer icon.