Installing a Window Air Conditioner

That's exactly what I was wondering about, that you so much for helping me!

You risk your compressor failing. It is a balanced mechanism and having it side ways will eventually cause problems. This may not be true with newer model AC units (I am not familiar with any technological break throughs, if there are any).
I wouldn't chance it. If I was in this situation I would try to trade with someone who has a smaller unit that could utilize a larger one or I would buy a smaller unit and attempt to sell the larger one to get the money back for the smaller.