Hey milhowz,
I'm sorry you're running into this issue with the administrator name. You can absolutely get your data back. The easiest way, in my opinion, is to use a LiveCD A LiveCD is a CD with an operating system installed on it. The operating system runs directly from the CD and does not have to be installed to the hard drive, allowing you to access your hard drive just like a USB flash drive.
The one I would recommend using is Knoppix. See this thread on using Knoppix to recover files.
Once you've got the files transferred over to an external hard drive, you can then try to change the admin name back, if you want. Try these suggestions for that. Otherwise, you may have to reinstall Windows. Let me know once you've got your files transferred to an external hard drive or if you have any questions on that.
I'll keep an eye out for your reply :)