I want to move my downloads to another server

[DrByte]

Is there a way to write a code so that zc can use a separate path to get the downloads?

Only if you want to rewrite a significant portion of the guts of the download code.

Perhaps you misunderstand what I mean by PCI compliance. This is a new requirement that all MC and Visa cards are requiring.

It's not new. It's been around for awhile. You'll see many discussions elsewhere on the forum about the same topic.
You'll also see that several of the Certified Hosts are already PCI-compliant, even with their "shared" accounts.

However, with my hosting server the cart is listed on, it can be moved to another dedicated server that iwill make the store PCI compliant.

If you look carefully, you'll realize that *if* they can put you on a dedicated server and suddenly you're compliant, then the issue is clearly not related to the Zen Cart software, but rather is tied to the shared server where they had/have you.

The problem is that particular server only has a limited amount of space and it doesn't have enough space to store all the download files they sell on the cart.

Maybe you're with the wrong hosting company.

What they need is a way to be able to store the downloads on a different location that isn't as limited, which is why we were looking into seeing if there was a way to switch the path or write something where they could have the downloads accessed from another location, rather than the default.

As mentioned above, you can do it, but it'll be less expensive to move to a host that's already PCI-compliant than to hire someone to rewrite the code to work with the less-than-optimal makeshift approach offered by your hosting company.