Melissa Hernandez, I am not sure if you can fix it for free:-) the red X is most likely caused by your Hard drive failing. You can verify this by putting your iPod classic in Diagnostic mode and see what the HDD test will reveal. "Take your iPod and place your right thumb on the centre SELECT button and your left on the top MENU button. Press down both thumbs for about 6 seconds until your iPod reboots. Immediately move your left thumb around to the rewind button |<< on the left and hold this down together with SELECT for a further 6 seconds. Your iPod should now switch into Diagnostic Boot mode. " take a note of the results. BTW it may fail on the FW (Firewire test as well, but that is normal since you might not have a firewire connection) If it indeed does fail I am sorry to tell you that you will have to replace your hard drive. it's anything but free. The instructions for the repair are here.
Now there is a chance, that your drive is just stuck. they do that sometimes. I do not like to bring this up since I do not believe that it is a good idea, but your can try to slap your iPod on the back side, and you got to slap hard and sometimes more than once. This may free up a stuck drive. It is at best only a temporary fix, and only works if your drive is stuck. It does not fix your drive. Hope this helps, good luck.