Can't run apt-get update, package files cannot be parsed/opened

Hi guys

So recently I've been trying to run apt-get update and have been getting this error:

Reading package lists... Error!
E: Read error - read (5: Input/output error)
E: The package lists or status file could not be parsed or opened.

I've seen a couple people who have had similar problems but I cant seem to find one that has a step-by-step explaination (I'm pretty new to Linux). Hope I can get some help to fix this problem, and thanks!