Replacing / removing Hard drives



please help,

I believe I have a corrupt HD but it is in the vertical HD cassette at the back of my G4... I know this might sound silly but although I can remove the casette under the disk drives. I don't seem to be able to remove the vertical cassette even to check it.

I would appreciate any help

It sounds like you are talking about the cover/slider that encases the drive. You should see some screws at the sides and or bottom.
Sounds like you have an MDD single processor Mac...if so, I have the same computer.

One thing that's missing in Apple's procedure for removing HD's at the rear location is that a screw at the top of the HD mounting bracket must first be removed. Then the Apple procedure for releasing and removing the HD's can be used.

Look for it and you will surely find it,