If you have a autorun.inf virus on your memory card/USB stick the anti virus software on your PC may not allow access in order to stop it from spreading.
First you need to disable autorun feature on Windows operating system :
Follow steps in link :http://www.redmondpie.com/how-to-disable-autorun-autoplay-in-windows-7-and-windows-8/
After disabling the feature you will have access to your memory card/USB stick. The next step is to delete autorun.inf virus file hidden on your memory card/USB stick. But first you need to make the hidden virus file visible.
Follow steps in link to show hidden system files :http://www.bleepingcomputer.com/tutorials/show-hidden-files-in-windows-7/
Now navigate to your memory card/USB stick you should see the autorun.inf file - DELETE IT.
(If it doesnt allow you to delete it - restart the PC in safe mode by pressing F8 on start up and choosing safe mode and try again)
Back up your files on the memory stick/USB stick to your PC and to make sure the virus is gone from the memory stick/USB format it using your PC.
Dont to forget re-hide your system files to prevent accidental deletion.