Hello forum, I'm very much a newbie so please bear with me. I had a 1 TB HDD in a D-Link DNS-323 NAS which I then put into my Windows 7 machine. I believe the drive is formatted via Linux; because of this it wasn't recognized by my Windows computer. In order for it to become recognized I changed it from a simple drive to a dynamic drive; now I'm fully unable to access the data on it. Can anyone recommend a fix for this?

You have made a big problem from a little spot with this movement.

The general problem is, you don't know the original FS type and in this way, you don't know wich program can help you....
In this case, i can suggest to you 1+2 thing:

1. and most important get another one 1TB empty drive, and MAKE A RAW SECTOR COPY before you do anything!!!

2a, try download various linux fs-supported recovery programs, and try to find what you can. (you have about 10% chance for success)
2b, seek for professional help. (>99% for success.)

Regards,
Janos