Does it or does it not fit?

You mean the measure of your "bare" desktop doesn't exceed 45"?

I really don't understand why a regular someone nowadays would insist on using a desktop as a travel computer. You don't necessarily have to get out and buy yourself a notebook or netbook, BTW, a netbook can be quite inexpensive these days. something less than $200. Your fiance and/or friends don't have a computer that you can use once you get over there since he lives there?

If what you need is the files/data on your desktop, you can just use a USB drive or something that is extremely portable and non-bulky. Unless there's some special softwares/programs that you must use but only have in your home computer.

Anyway, good luck getting onboard with your "desktop carry-on" when flying Delta.