Cannot drag & drop folders or files

I'm using XP Pro, P4-2.4GHz, C: drive for software and D: for patches, upgrades and overall data. When I drag files or a folder on D:, they make the transfer to the destination folder but the files and folders are not accessible. I cannot open any of the files I had previously dragged and dropped. My work-around, for existing files, is to copy the files to C:, then copy to where I want on D:, then delete the old files on C: & D:. When I backup with Backup MyPC, the bad files aren't archived. I get error message "The file 'D:\Jokes\Joke A Day.txt', as specified in the execution parameters, cannot be opened." or "Access denied: you do not have rights to do this." This is with all file extensions, text or graphics. Even manipulating the properties of the file doesn't help. I'm completely locked out. I have recently changed my D: drive to a 200GB, 7200RPM, and restored the backup with no overwrite and the problem is still there. Thank you.