Windows 7: xp doesn't read win 7 word files

Pweegar & Logicearth:

Just spent the morning fiddling around, trying to isolate the problem. I may have solved it, but have no idea why... . Both those suggestions seemed good -- maybe a lock on the file that wasn't releasing (I had closed the program when trying to view/open it on the XP machine). I found that .doc files would save clearly on both os's and .docx started saving correctly (for xp) in other subdirectories, which just added a layer of more weirdness to it (but docx still glitched in the original directory LARO_EA). Then I changed the name of the original folder, taking out the underscore (_) but leaving it in uppercase. Shazzam! It's now saving and visible in both xp & windows 7. So it would appear that the underscore causes some sort of hiccup in the machine (hiccupus ex machina?).

So, I've solved the problem, I guess, but still have a couple of questions if anyone ever runs across an answer:

1) What's the problem with the underscore: LARO_EA vs LAROEA, when saved in Windows 7 (but not xp)?

2) What are those .tmp files? That seems diagnostic. Are they a function of Word 2007. They're all about the same size -- many are equal. It seems that that naming scheme should tell us something??

Many thanks for everyone's help here. If anything occurs to you, I'd still be interested.

George