It can't find flevel.lgp. Which version (language) of FF7 are you playing? Check if you actually have flevel.lgp in this folder (C:\Program Files (x86)\Square Soft, Inc\Final Fantasy VII\data\field\).
In case you don't know how to check I'll explain (just in case, I'm not suggesting you don't know how).
1. Open "My Computer" start -> Computer.
2. Open C: (you've may have named it something, but it should read "C:" somewhere). Double click to open obviously.
3. Then open these folders in order: Program Files (x86) -> Square Soft Inc -> Final Fantasy VII -> data -> field
4. Once in the field folder you should see a file named something like flevel.lgp. You may not see the extension (.lgp), but that doesn't matter.
To my knowledge the different language versions name it differently. For instance, ackording to my knowledge, in the french version it's called fflevel.lgp. I didn't know this 'til after I've made the patch, assuming the file names were equal in each version.
5a. IF you find a file with similar name (i.e. fflevel.lgp. And, remember, you may not see the extension, the .lgp part. It doesn't matter), rename that file to flevel.lgp (or flevel IF you don't see the extension). To rename a file, simply right-click, select rename and type in the name.
OR
5b. The file does not exist... which does not make sense since you obviously played it. If that's the case you should reinstall the game (uninstall 1st). EDIT: FULL INSTALL!
My mod and Ali's graphic driver is fully compatible. It doesn't matter which of these you install 1st.
Hope this helps. Let me know if it works or not.
EDIT2:
6. Obviously, if you found and renamed a flevel it's name needs to be restored back as it originally were before playing. If not the game will probably crash.