External hard drive won't open jpeg files

I've had the same problem off and on and it seems it's related to the amount of space I have on my C: drive. My external hard drive won't open my picture files (most all jpegs) but it will open other files easily. It won't even open the folders they're in. I only have 11 GB of space on my hard drive (hence the reason I bought this) and when I was down to like 240 MB it wouldn't let me do anything PERIOD because of low disk space. Anyway, I moved pictures to the external drive (25 GB worth apparently) and then it opened just fine. I added Microsoft Publisher to my computer and now the folders or files won't open again. Is the external drive dependent on a certain amount of disk space for it to be able to open certain large files/folders? How do I fix this because I can no longer access my pictures no matter what I do--tried dragging to desk top, still won't open. I'm on the phone with tech support but it's taking forever and I don't think I'll have time to wait for them today. Thanks so much!