Um, so how does one break into this dull field?
* Learn systems, and programming, and all that other crap but you were going to do that anyway. Linux and the cool stuff are fine, just remember to learn Windows too. Enjoy it. It won't be the worst system you'll use by any stretch.
* Use whatever system they give you. You'll learn something from everything you use. If someone pulls a 1978 CADO Systems CAT III out of a closet and needs you to retrieve financials from it, you'll learn the wonders of 8086 multi-user programming and hashed files.
* Take an accounting class. Hell, take two. Business classes are helpful as well. See things from your employer's and their client's perspective. Look at double-entry bookkeeping as a wonderful checksum and transaction based system. Speak to them in their own language.
* Try data entry for a spell. Barring that, go quietly watch your users work. Don't tell people how to use your software, watch how they use it. Nobody wants to click a mouse when they're being read columns of numbers over a telephone by a busy accountant.
* Make yourself useful. If you're not useful there, go find somewhere else to work.