How to get the rest of my email folders to import over??

Does anyone know if there is a "folder limit" or "size limit" in Windows Mail?? I have hundreds of folders with e-mails located inside and when I had to rebuild Windows Mail because my spell check didn't work, I backed up my e-mail folders in a empty folder on my C drive as well as on my back up drive and when I went to import them all back, I only was able to import a portion of them.. Others, when I go to import them manually, they say they imported over, but when you open the import file, nothing is there.. Any suggestions on how to get the rest of my folders to import over?? Thanks kolmtiger