Ilovepath,
According to what someone has posted above, it looks like Windsor and AUA both haven't been approved in several states. Each state (individually) gets to make its own rules about what credentials you have to have to be licensed there. Some won't approve licenses for folks from certain schools. You need to be really careful, and at least to check with the medical boards of several states where you'd consider practicing in the future, and make sure these school(s) are accepted by them before you even think of going there.
windsor, from what I know, isn't really that reputable. The other school that you mentioned I don't know.
Keep in mind also that certain states require that you did most of your med school at the same school/location. I think California has some sort of rule like that. I mean, it seems you are looking to get credit for most of your 3rd year, but the thing is, a lot of states might not accept your MD from Windsor anyhow (either because they don't accept that place as a legitimate medical school, or because they won't accept a graduate who did only slightly >1 year at the school where he graduated). I know you want to avoid paying more money, but you have to think about what you are paying money FOR. You are paying money so that you'll have a shot at getting a residency, not just graduating. Graduating and then not being able to get any residency leaves you with an almost useless degree, assuming that practicing in the USA is what you want.
Just as an example of what states may require, you can check the web site of the California Medical Board. They have a list of approved medical schools on there. It's a long list containing many foreign schools. They also have a list of schools that they have specifically disapproved...I don't see Windsor and AUA on there, but St Matthews is on the disapproved list (for example). Here's the link for the list of "approved" schools:
http://www.medbd.ca.gov/applicant/schools_recognized,html
Another thing you need to think about really, really hard is that all states that I know of have a lot of questions on their medical license applications that you have to answer. One of them is always a question about whether you have ever been dismissed or withdrawn from a medical school. If you answered yes then you have to explain why, etc. I don't have any idea of the circumstances of why you left your old school, but I'm pretty sure they'll investigate that. I am worried it might hurt your chances for getting a license anywhere, especially if your old school tells them something unflattering about you. And you don't want to do another couple years of school and then residency for a couple of years and then find out you can't get a license anyhow - that would suck. Also it might be hard to get a residency to take you if they find out about your history...some I guess depends on why you left your old school and how it reflects on you.
You might want to get advice from a lawyer experienced with your type of case before you re-enroll in medical school - it might be hard fo find one but I think there are some. You just don't want to end up wasting your time in any school. Above all I wouldn't be in a super big rush to just go somewhere...you want a degree that means something, and to be sure you have a chance at actually practicing or what is the point? Otherwise it might be better to just go into some type of other business or health care management, etc.