Drawing file not valid

[Dubya D]

I searched for this issue before I made this post. Everything I saw pertained to not being able to open newer versions of a drawing in older software.
I'm having a problem opening drawings back to r13 using AutoCAD 2007. Any idea how to fix this?

[rkmcswain]

When you try and open an r13 drawing in 2007, it says "invalid drawing"?
Can you open it in R13? If not, maybe it really is a corrupt DWG file.

[Dubya D]

I inherited some drawings from a retired drafter. I loaded them on my computer and have been able to access them in the past. In the last couple of months for some odd reason I get the error message. I no longer have r13 on my computer. The drawings I have range from r13 to 2007.