Adding Extra Fields and Shopping Cart won't show up!

Version: 1.3.8a
Almost fresh install
Custom Theme
Hello! I choose Zencart after playing around heavily with the other avaliable options - Cubecart, OSCommerce, etc. Thus far, Zencart has proven to be the most easy to customize and edit.

However - and this is a two-parter question, I've run into a couple of issues.

First, the shopping cart module refuses to show up in either of the right or left sidebars. They haven't been edited at all except to remove the original colors, and other modules show up exactly where they're supposed to be. These are it's settings:
Box Name: shopping_cart.php
Left/Right Column Status: ON
Location: (Single Column ignores this setting) RIGHT
Left/Right Column Sort Order: 34
Single Column Sort Order: 1
Single Column Status: OFF

What should I do to fix that?

There's also another issue - during checkout, I need to add a field for a serial number to various but not all of my products. Which mod would be best for that?

The shopping cart sidebox doesn't show up until there's something in it by default, though you can change that in admin.

Fixed the shopping cart issue, but what about the other mod issue? I really need that extra textfield for a serial number.

When you go to the checkout there is already an extra field for Special Instructions or Comments About Your Order , wouldn't that suffice if you changed the text?

No, unfortunately... what if that was needed for something else? Changing the wording would remove that.

Are you already using the Products Model: for something else?

No, I'm not. I'm trying to keep all products separate from eachother in all aspects.

In which case, you've lost me (easily done). I'd have thought that if you're not using it then it IS that 'extra' field you need, just add the serial number in there when you add the product initially.

I'm maybe misunderstanding what it is exactly you're after though :wacko:

I'll try to do it via the extra field at first, and hope customers aren't too confused!