Unable to access DVD+RW

I am encountering a strange problem with reading a DVD+RW I created containing a backup of all my personal files. I formatted and burned the disk using DLA(Drive Letter Access) so that I could add/remove files individually as you would a floppy. At first everything worked fine, so I kept adding more and more files until I had just over 4GB of data. That's when the problems began.

I inserted the disk into the DVD drive, and is is acknowledged. The properties correctly state how much space has been used, and that approx 600MB remain free. I can open the dive and see the three primary folders, but upon opening them I cannot see any of the files (they are not hidden). I tried selecting all and copying it to my hard drive, but the subfolders are not copied. I also tried using another computer to access the disk, but the same problem occurred.

However, I remembered the exact directory and name of one of the MS Word files. I entered it into the address bar and the file opened in Word. I was also able to save the changes to the DVD, then open the file on the second computer. The problem is I only know the one file name, whereas there are hundreds on the DVD. Is there any way of simply copying all of the files (mostly Powerpoints) on the DVD onto my hard drive so that I can use the disk for target practice?

I have: AMD Athlon64 3300+, 1GB PC3200 SDRAM, 4GB paging file, 160GB HD (50GB used), and a 16X Lite-On DL DVD+/-RW drive. With that, I can't imagine it being a memory or space issue, so I'm assuming it's a flaw with Windows XP Pro's explorer reading large Powerpoint files on a disk formatted/burned with DLA. (Although the explorer in MS Word and Powerpoint can't see the files/subfolders either.)

Thanks for your help,
John